The Quran

وَرَبُّكَ أَعلَمُ بِمَن فِي السَّماواتِ وَالأَرضِ ۗ وَلَقَد فَضَّلنا بَعضَ النَّبِيّينَ عَلىٰ بَعضٍ ۖ وَآتَينا داوودَ زَبورًا

Muhammad Asad

seeing that thy Sustainer is fully aware of [what is in the minds of] all beings that are in the heavens and on earth. But, indeed, We did endow some of the prophets more highly than others¹ -just as We bestowed upon David a book of divine wisdom [in token of Our grace].²

This seems to be an allusion to the role of Muhammad as the Last Prophet (Zamakhshari, Baydawi): despite his personal inability to "determine the fate" of the people to whom he conveyed God's message, that message is destined to remain alive forever.
I.e., just as David's "book of divine wisdom" (the Psalms) had outlived the glory of his earthly kingdom, so will Muhammad's message, the Qur'an, outlive all the changing fortunes of his followers.