1. Sincerity in Tawheed.
Allaah's Messenger (saw) said, "A servant never says: "La ilaha illa Allaaha" sincerely except the doors of heavens are opened for it until it reaches the Throne (of Allaah)" (Sahih ul-Jami', no. 5524).
He (saw) also said, "Indeed Allaah has forbidden the fire from the one who said, "La ilaaha illa Allaaha" seeking thereby the Face of Allaah." (part of a hadeeth by al-Bukhari and Muslim).
2. Sincerity in Intention.
Allaah's Messenger (saw) said, "Indeed actions are (judged) by intentions (behind them) and every man shall receive (for his action) only that which he intended". (al-Bukhari, Muslim).
3. Sincerity in the prayer.
Allaah's Messenger (saw) said, "There is no person who performs wudhu, beautifying it, then prays two rakah concentrating therein with this heart and face except that Paradise becomes obligatory for him." (al-Albaani declared it sahih in Sahih ul-Jami' no. 5678).
He (saw) also said, "There is none amongst you who, when he goes to perform ablution, rinses his mouth and spits out the water and sniffs the water up his nose and then expels it except that the sins of his face, mouth and nose flow from him. Then when he washes his face as he has been commanded by Allaah, the sins flow away from him from the sides of his beard with the water. Then, when he washes his arms up to (and including) the elbows, the sins of his hands flow away with the water from the extremes of his fingertips. Then he wipes his head as Allaah has commanded him and the sins of his head flow away from him from the ends of his hair with the water. Then he washes his two feet up to (and including) the ankles and the sins of his feet flow away with the water from the ends of his toes. If he then stands, prays, praising Allaah, extolling Him, glorifying Him with what He is deserving of and empties his heart for Allaah, he will walk away from his sins in the same state as the day his mother gave birth to him". (Muslim and others).
4. Sincerity in prostration.
He (saw) said, "there is no servant who makes a prostration for Allaah except that Allaah writes a good deed for him, removes from him an evil deed and raises his station by one degree. So increase in making prostration." (al-Albaani declared it sahih in Sahih ul-Jami', no. 5618).
5. Sincerity in the prayer of Ramadhan
He (saw) said: "Whoever stood for prayer in Ramadhan out of faith and expectation of reward will have his previous sins forgiven". (al-Bukhari and others)
The same applies for prayer during Laylatul Qadr (al-Bukhaari and others).
6. Sincerity in leaving one's house for the prayer.
Allaah's Messenger (saw) said, "The (reward of the) prayer of a man in congregation is increased by twenty five degrees over his prayer in his house or in his market (i.e. his trading place). That is when he performs wudhu and beautifies it, then leaves for the masjid desiring nothing but the prayer and nothing makes him leave his house except the prayer. He does not advance a step (towards the masjid) except that he is raised by one degree and one sin is removed from him. When he enters the masjid he is engaged in prayer as long as the prayer is what keeps him back. The angels engage in prayer as long as the prayer is what keeps him back. The angels do not cease to send prayers upon him so long as he is engaged in his prayer. They said, "O Allaah! Send prayers upon him. O Allaah! Show mercy to him." And a man never ceases to be engaged in prayer so long as he is waiting for it."
In another narration, "(The angels say): O Allaah! Forgive him, O Allaah! Turn to him so long as he does not cause any harm or emit something (to nullify his ablution)." (al-Bukhari and Muslim).
7. Sincerity in Fasting.
Allaah's Messenger (saw) said, "Whoever fasted the month of Ramadhan out of faith and seeking reward, his past and future sins will be forgiven." (Saheeh ul-Jami', no. 6201).
He (saw) also said, "Whoever fasts a day in the path of Allaah, Allaah will make the Hellfire distant from him the length of a hundred years journey". (an-Nasa'i, al-Albaani declared it hasan in Saheeh ul-Jami', no. 6206)
He (saw) also said, "Whoever fasted a day in the path of Allaah, Allaah makes between him and the Fire a trench like the one between the Heavens and the Earth." (at-Tirmidhi, Saheeh ul-Jami', no. 6209).
8. Sincerity in Giving Charity
The hadith regarding the seven who will receive Allaah's Shade on the day where there will be no shade except His and amongst them is: "..and a man who gives charity and conceals it to such an extent that his left hand does not know what his right hand has spent." (Muslim).
Allaah's Messenger (saw) also said, "Charity which is given in secret extinguishes the anger of the Lord and maintaining the ties of kinship increases one's age". (Saheeh ul-Jami' no. 3691).
9. Sincerity in Performing Hajj
He (saw) said, "Whoever performed Hajj for the sake of Allaah, did not behave in an obscene manner and was not disobedient, will return in the same condition as the day his mother gave birth to him". (al-Bukhari and others).
10. Sincerity in Seeking Martyrdom
Allaah's Messenger (saw) said, "Whoever asked Allaah to be killed in the path of Allaah truly out of his heart, Allaah will give him the reward of a martyr even if he died on his bed." (Muslim).
11. Sincerity in guarding the frontiers of the Muslim lands
Allaah's Messenger (saw) said, "Whoever guards (The Muslim frontiers) for a day and a night for the sake of Allaah receives the rewards of a month's fasting and prayer. And whoever died while guarding the frontier will have a reward similar to that, sustenance will be made to come to him and he will be made secure from trials." (an-Nasa'i, al-Haakim in al-Mustadrak. Saheeh ul Jami', no. 6135).
12. Sincerity in Equipping Someone for a Military Expedition.
Allaah's Messenger (saw) said, "Whoever supplies and equips another (doing that) for the sake of Allaah in going upon a (military) expedition, will have the reward similar to the one whom he equipped without any of the latter's reward being diminished". (Ibn Maajah, al-Albaani declared it saheeh in at-Targheeb 2/96)
13. Sincerity in Repentance
Abu Sa'eed al-Khudri (ra) reports that Allaah's Messenger (saw) said, "There used to be a man from among those who came before you and who had killed ninety-nine men. He asked about the most knowledgeable person of the people of the earth and he was directed to a monk. He caem to him and said that he had killed ninety-nine men so was there any chance of repentance for him. The monk said, "No". So the man killed him and completed the number of his victims to one hundred. Then he again asked about the most knowledgeable of the people of the earth and he was directed to a scholar. He explained to him that he had killed one hundred men and asked whether there was any chance of repentance for him. He said, "Yes, and who is there that stands between Him and repentance? Go to such and such a land since there are a people ther who worship Allaah ta'ala and go and worship Allaah along with them. Do not return to your homeland as it is an evil place." The man left for the place he had been directed to and when he had reached half-way, death came to him. The angels of mercy and the angels of punishment began to argue about him and the angels of mercy said, "He came repentant to Allaah, directing his heart towards Allaah the Exalted" and the angels of punishment said: "He never did any good". Then another angel came to them in the form of a man and acted as an arbiter between them. He said, "Measure the distances of the two lands (from the place he died) and whichever of the two is nearest to him will determine his fate." They measured the distances and found that he was closer to the land he was travelling to and so the angels of mercy took his soul" (al-Bukhari, Muslim).
14. Sincerity in Weeping from Fear of Allaah and in the Remembrance of Allaah
One of the seven who will receive Allaah's shade on the day on which there is no shade by His is ".. a man who remembers Allaah when he is alone and his eyes shed tears". (an-Nasaa'i, al-Haakim in al-Mustadrak, Saheeh ul-Jami', no. 1428)
24. Sincerity in Loving and Visiting for the Sake of Allaah
Allaah's Messenger (saw) said, "Whoever is delighted (ie eager) that he should taste the sweetness of faith let him love a man, not loving him except for the sake of Allaah". (Ahmad in al-Musnad, al-Haakim, Saheeh ul-Jami', 6164).
Abu Hurayrah (ra) reports that Allaah's Messenger (saw) said, "There was a man who set out to visit a brother of his in another town. Allaah had prepared for him along his way an angel (in the form of a man). When he met him he said, "Where do you intend to go?" The man replied, "I intend to see my brother in this town." The angel said, "Do you have any favour which he owes you?" He said, "No, but I love him for the sake of Allaah ta'ala." The angel said, "I am a messenger of Allaah sent to you to inform you that Allaah loves you as you have loved your brother". (Muslim).
25. Sincerity in One's Intention Even If It Is Not Acted Upon.
Allaah's Messenger (saw) said, "Whoever asked Allaah to be killed in the path of Allaah truly out of his heart, Allaah will give him the reward of a martyr even if he died in his bed". (Muslim).
26. Sincerity in Renouncing the Dunya and in Humility
Allaah's Messenger (saw) said, "Whoever abandoned (a certain type of) clothing out of humility to Allaah, even though he was capable of (affording and wearing) it, Allaah will call him out in front of all the creation and put him to option about any of the garments of faith that he wishes to wear." (at-Tirmidhi, Saheeh ul-Jami' no. 6021).
He (saw) also said, "Whoever humbled himself for Allaah, Allaah will raise him". (Abu Na'eem in al-Hilyah, from Abu Hurayrah, Saheeh ul-Jami',. no. 6038)
27. Sincerity in Building Masajids
Allaah's Messenger (saw) said, "Whoever built a mosque seeking the Face of Allaah by it, Allaah will build for him what is equal to it in Paradise." (al-Bukhari).
28. Sincerity in Visiting the Masjid of the Messenger (saw) for learning and teaching.
"Whoever came to this masjid of mine and did not come except to learn or teach goodness, (then he) is in the same position as the one who struggles and fights in the way of Allaah. Whoever comes for a purpose other than that, is in the same position as a man who (stands) looking at the enjoyment of others". (Ibn Majah, al-Haakim in al-Mustadrak, Saheeh ul-Jami' no. 6060).
29. Sincerity in Following the Funeral Procession of a Muslim
"Whoever followed the funeral procession of a Muslim out of faith and expectation of reward and remained with it until he performed the funeral prayer (for the deceased) and until the burial, will return while having obtained the reward of two qeeraat, each qeeraat is equal to the mountain of Uhud. And whoever performed the funeral prayer, returning before the burial, will receive one qeeraat of reward." (al-Bukhaari).
30. Sincerity in Feeding Someone
Allaah ta'ala said concerning the sincere:
"And they feed for the sake of Allaah, the indigent, the orphan and the captive, saying "We feed you only for the Face of Allaah, no reward do we desire from you, nor thanks." (76:8-9)
A'ishah (ra) said, "I offered Allaah's Messenger (saw) a sheep and he ordered for it to be divided amongst some people. When the servant returned, Aisha (ra) said, "What did they say?" The servant replied, "They said, "May Allaah send blessings amongst you". Aishah then replied, "And may Allaah send blessings amongst them. We will return to them similar to what they have said to us and our reward (for the food) remains with us". (Saheeh ul-Kalimut-Tayyib, no. 238).
It is from the perfection of the ikhlaas of Aishah (ra) that she did not expect anything from them, not even supplication.