"And We gave him glad tidings of Isaac, a prophet among the righteous," meaning: among the righteous prophets.
﴿وَبَشَّرْنَاهُ بِإِسْحَاقَ نَبِيًّا مِنَ الصَّالِحِينَ﴾ يُرِيد: من صَالح الْأَنْبِيَاء