As-salam `alaykum wa rahmatu Allah.

Thank you for your question.

If your question is regarding helping you research some Prophetic hadiths (sayings) on ikhlas (sincerity of faith), that should not be hard.

Still, in order not to just throw all the hadiths related to the issue without canonical and categorical understanding—an authentic practice in traditional Islam—we should start off with the hadiths that reveal the essence of ikhlas, devotional sincerity.

In that, we should start off with the notable first hadith in the renowned manual Forty Hadith by the eminent and masterly Imam Al-Nawawi (may Allah be pleased with him). The hadith is narrated on the authority of Commander of the Faithful `Umar ibn Al-Khattab (may Allah be please with him), who said that he heard the Messenger of Allah (peace be upon him) say:

“Deeds are (judged) by intentions (niyyah), so each man will have what he intended. Thus, he whose migration (hijrah) was to Allah and His Messenger, his migration is to Allah and His Messenger; but he whose migration was for some worldly thing he might gain, or for a wife he might marry, his migration is to that for which he migrated” (Al-Bukhari & Muslim). Please refer to FortyHadiths.com

The basic hadith sets the exoteric realm of actual ikhlas: it is the relation to intention, and actions as a product of that. Still, even as many books related to these adab (manners) and values, all three—intention, sincerity, and truth—seem to be interlocked. There is no doubt that the essence of sincerity is between intention and truth.

Still, as for the essence of ikhlas in itself, it was narrated in The Musnad by Imam Ahmad that the Prophet (peace be upon him) narrated that he asked Jibreel, and then he asked Allah (majestic in His praise) about sincerity, and He answered, “Sincerity is a secret of secrets I stored in the heart of the ones I love among My servants.”

So, let’s understand that ikhlas in its nature is a secret, stored and treasured. We will find out then that the rest of known hadiths will then either deal, in principle, with the secretive nature of ikhlas or with its being treasured.

Let it be noted that the following hadiths are taken from the magnum opus of the most-respected and highly esteemed Imam Al-Ghazali, The Revival of Religious Sciences, which I highly recommend for further reading on the subject matter (Book 37).

The first hadith states that “there should be no envy for three matters related to the heart of a Muslim: … devoting works for Allah” (At-Tirmidhi). This hadith shows the preciousness of such a trait. A comment on this hadith says, “Whoever works for Allah’s sake sincerely for forty days, the fountains of wisdom will flow from his heart to his mouth.” (Narrated by Ibn `Adii and, from the same chain, Ibn Al-Jawziah in Al-Mawdo`at through Abu Musa.) In this hadith, the fruits of ikhlas are presented.

There is also a hadith narrated by Al-Nasa’i that the Prophet (peace be upon him) said, “The angels lift the works of a servant, multiplying it and purifying it. Then Allah, majestic in His praise, reveals to them: ‘You are custodians over My servant’s work and I am watchful over what’s inside him. My servant did not act with sincerity; take him to Sijjin (a low place in Hellfire).’ And they—the angels— lift the works of a servant thinking of decreasing its worth. Then it is revealed to them: ‘You are custodians over My servant’s work and I am watchful of what is inside him. Multiply it and make him in `Iliyin (a high place in Paradise).’”

If anything, this hadith shows the ultimate secretive nature of ikhlas between the servant and Allah, majestic in His praise.

May Allah increase your and our ikhlas.

Thank you and please keep in touch.

Salam.

N.B.
* AAI staff shared in translating and paraphrasing hadiths mentioned in this answer.

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