The Book of Faith
حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، وَإِسْحَاقُ بْنُ إِبْرَاهِيمَ، قَالَ قُتَيْبَةُ حَدَّثَنَا جَرِيرٌ، عَنِ الْمُخْتَارِ بْنِ فُلْفُلٍ، عَنْ أَنَسِ بْنِ مَالِكٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " أَنَا أَوَّلُ النَّاسِ يَشْفَعُ فِي الْجَنَّةِ وَأَنَا أَكْثَرُ الأَنْبِيَاءِ تَبَعًا " .Anas b. Malik reported:The Messenger of Allah (ﷺ) said: I would be the first among people to intercede in the Paradise and amongst the apostles I would have the largest following (on the Day of Resurrection)
From Sahih Muslim, whose reports the scholars accept as authentic.