Muhammad bin Ka'b says that Sayyiduna Mu'awiyah (may Allah be pleased with him) said from the pulpit of the Messenger of Allah (peace and blessings be upon him): "Allah Almighty grants understanding of the religion to whomever He intends good for." Sayyiduna Mu'awiyah (may Allah be pleased with him) said: I heard these words from the Messenger of Allah (peace and blessings be upon him).
Explanation: From this blessed hadith, it is understood that deep understanding of the religion (tafaqquh), its comprehension, and insight into it are a great good and a supreme blessing, and this is granted only to that fortunate person with whom Allah, the Exalted, is pleased and for whom He intends good.
In this hadith, there is great glad tidings for the person whom Allah, the Exalted, has endowed with understanding of His religion. At the forefront of understanding the religion is the recognition (ma‘rifah) of Allah, the Exalted, and His oneness (tawhid). Allah, the Exalted, says:
﴿فَاعْلَمْأَنَّهُلَاإِلَٰهَإِلَّااللَّهُ﴾ (Muhammad: 19) “So know that there is no (true) deity except Allah.”
If one attains understanding of tawhid, then he has attained good and virtue; but if he does not even understand tawhid, then no matter how many sciences he may know, he is deprived of good and virtue. These sciences may be beneficial for the world, but not for the Hereafter.