"And indeed, they are among the chosen (al-mustafayn) with Us," meaning: the selected ones, whom Allah chose for prophethood.
﴿وَإِنَّهُم عندنَا لمن المصطفين﴾ يَعْنِي: المختارين , اخْتَارَهُمْ اللَّه للنبوة.