Sahih Muslim Book - 38, Hadith - 5593

حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى ، وَمُحَمَّدُ بْنُ بَشَّارٍ ، قَالاَ : حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ ، حَدَّثَنَا شُعْبَةُ ، سَمِعْتُ قَتَادَةَ ، عَنْ سَالِمٍ ، عَنْ جَابِرِ بْنِ عَبْدِ اللهِ ، أَنَّ رَجُلاً مِنَ الأَنْصَارِ وُلِدَ لَهُ غُلاَمٌ ، فَأَرَادَ أَنْ يُسَمِّيَهُ مُحَمَّدًا ، فَأَتَى النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَسَأَلَهُ ، فَقَالَ : أَحْسَنَتِ الأَنْصَارُ سَمُّوا بِاسْمِي ، وَلاَ تَكْتَنُوا بِكُنْيَتِي.

It was narrated from Jabir bin 'Abdullah that a boy was born to an Ansari man and he wanted to call him Muhammad, so he came to the Prophet (s.a.w) and asked him, and he (s.a.w) said: "The Ansar have done well; you may call yourselves by my name and you do not call yourselves by my Kunyah."