The Book of Repentance
حَدَّثَنِي عَبْدُ اللَّهِ بْنُ مَسْلَمَةَ بْنِ قَعْنَبٍ الْقَعْنَبِيُّ، حَدَّثَنَا الْمُغِيرَةُ، - يَعْنِي ابْنَ عَبْدِ الرَّحْمَنِ الْحِزَامِيَّ - عَنْ أَبِي الزِّنَادِ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " لَلَّهُ أَشَدُّ فَرَحًا بِتَوْبَةِ أَحَدِكُمْ مِنْ أَحَدِكُمْ بِضَالَّتِهِ إِذَا وَجَدَهَا " .Abu Huraira reported Allah's Messenger (ﷺ) as saying:Allah is more pleased with the repentance of His servant when he turns penitently towards Him than one of you would be on finding the lost camel
From Sahih Muslim, whose reports the scholars accept as authentic.