The Book of Oaths
حَدَّثَنِي مُحَمَّدُ بْنُ حَاتِمٍ، حَدَّثَنَا بَهْزٌ، حَدَّثَنَا شُعْبَةُ، حَدَّثَنَا سِمَاكُ بْنُ حَرْبٍ، قَالَ سَمِعْتُ تَمِيمَ بْنَ طَرَفَةَ، قَالَ سَمِعْتُ عَدِيَّ بْنَ حَاتِمٍ، أَنَّ رَجُلاً، سَأَلَهُ فَذَكَرَ مِثْلَهُ وَزَادَ وَلَكَ أَرْبَعُمِائَةٍ فِي عَطَائِي .Tamim b. Tarafa reported:I heard 'Adi b. Hatim say that a person asked that and then narrated (the hadith) like one (mentioned above), but he made this addition:" Here are four hundred (dirhams) for you out of my gift
From Sahih Muslim, whose reports the scholars accept as authentic.