Parents Of Prophet Muhammad
It did not lose its credibility because Muslims were there in his lineage before the holy prophet, and after the holy prophet began his preaching. In his prayers, he also mentions that among them who obey me, he is from, and the one who does not, God will judge him. See Sura Ibrhim 34-35 وَإِذْ قَالَ إِبْرَاهِيمُ رَبِّ اجْعَلْ هَٰذَا الْبَلَدَ آمِنًا وَاجْنُبْنِي وَبَنِيَّ أَن نَّعْبُدَ الْأَصْنَامَ ‎﴿٣٥﴾‏ رَبِّ إِنَّهُنَّ أَضْلَلْنَ كَثِيرًا مِّنَ النَّاسِ ۖ فَمَن تَبِعَنِي فَإِنَّهُ مِنِّي ۖ وَمَنْ عَصَانِي فَإِنَّكَ غَفُورٌ رَّحِيمٌ On the other hand, God had informed him that the promise he made with him about Imamat for his progeny will not be for those who will be Zalim. See 2; 124 وَإِذِ ابْتَلَىٰ إِبْرَاهِيمَ رَبُّهُ بِكَلِمَاتٍ فَأَتَمَّهُنَّ ۖ قَالَ إِنِّي جَاعِلُكَ لِلنَّاسِ إِمَامًا ۖ قَالَ وَمِن ذُرِّيَّتِي ۖ قَالَ لَا يَنَالُ عَهْدِي الظَّالِمِينَ