Tafsir of An-Nur 24:38

ليجزيهم الله أحسن ما عملوا

That Allah may reward them according to the best of their deeds, meaning, "They are those from whom We shall accept the best of their deeds and overlook their evil deeds.''

ويزيدهم من فضله

and add even more for them out of His grace. means, He will accept their good deeds and multiply them for them, as Allah says:

إن الله ﻻ يظلم مثقال ذرة

Surely, Allah wrongs not even of the weight of a speck of dust. (4:40)

من جاء بالحسنة فله عشر أمثالها

Whoever brings a good deed shall have ten times the like thereof to his credit. (6:160)

من ذا الذى يقرض الله قرضا حسنا

Who is he that will lend to Allah a goodly loan. (2:245)

والله يضعف لمن يشاء

Allah gives manifold increase to whom He wills. (2:261) And Allah says here:

والله يرزق من يشاء بغير حساب

And Allah provides without measure to whom He wills