The Book of the Merits of the Companions
حَدَّثَنَا هَدَّابُ بْنُ خَالِدٍ، حَدَّثَنَا سُلَيْمَانُ بْنُ الْمُغِيرَةِ، حَدَّثَنَا حُمَيْدُ بْنُ هِلاَلٍ، عَنْ عَبْدِ، اللَّهِ بْنِ الصَّامِتِ قَالَ قَالَ أَبُو ذَرٍّ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " غِفَارُ غَفَرَ اللَّهُ لَهَا وَأَسْلَمُ سَالَمَهَا اللَّهُ " .Abu Dharr reported Allah's Messenger (ﷺ) as saying:Go to your people and say that the Messenger of Allah (ﷺ) says: Ghifar (is a tribe) to whom Allah granted pardon, and Aslam (is the tribe) to whom Allah granted safety
From Sahih Muslim, whose reports the scholars accept as authentic.