[4:162] But those of them who are firmly rooted in knowledge, and the believers, believing in what has been revealed to you, and what was revealed before you, and those who observe the prayer; and pay the alms, and those who believe in God and the Last Day - to them We shall surely give a great wage.
[The verse refers to] the one who is firmly rooted in knowledge, the proof and judgement of which is not by blind following. Instead reflection (naẓr) has been put in its place to such an extent that there is no possibility of doubt in one's understanding (ʿaql).
It is said the one who is firmly rooted in knowledge ascends from the limit of pondering demonstrative proof (burhān) to attain the realities of clear evidence (bayān).
It is said the one who is firmly rooted in knowledge is one whose knowledge is practiced to the degree that he benefits from knowledge that is hidden from others, as in the tradition: To whoever practices what he knows, God grants knowledge of what he does not know.
[The phrase] those who observe prayer is given the grammatical accusative inflection to indicate the laudative. Prayer is given distinction among other acts of worship in that it follows [the mention of] faith in most passages in the QurÌān, and because God (s) gave the command for prayer directly to the Messenger (ṣ) on the Night of the Miʿrāj without the intermediary of Gabriel (ʿa), and because of other reasons.
A great wage: The great wage is that which increases commensurate with what the work deserves.