Muwatta Imam Malik Book of Judgements, Hadith 3

Yahya related to me from Malik from Abdullah ibn Abi Bakr ibn Muhammad ibn Amr ibn Hazm from his father from Abdullah ibn Amr ibn Uthman from Abu Amra al-Ansari from Zayd ibn Khalid al-Juhani that the Messenger of Allah ﷺ said, "Shall I not tell you who is the best of witnesses? The one who brings his testimony before he is asked for it, or tells his testimony before he is asked for it."

حَدَّثَنَا يَحْيَى، عَنْ مَالِكٍ، عَنْ عَبْدِ اللَّهِ بْنِ أَبِي بَكْرِ بْنِ مُحَمَّدِ بْنِ عَمْرِو بْنِ حَزْمٍ، عَنْ أَبِيهِ، عَنْ عَبْدِ اللَّهِ بْنِ عَمْرِو بْنِ عُثْمَانَ، عَنْ أَبِي عَمْرَةَ الأَنْصَارِيِّ، عَنْ زَيْدِ بْنِ خَالِدٍ الْجُهَنِيِّ، أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ " أَلاَ أُخْبِرُكُمْ بِخَيْرِ الشُّهَدَاءِ الَّذِي يَأْتِي بِشَهَادَتِهِ قَبْلَ أَنْ يُسْأَلَهَا أَوْ يُخْبِرُ بِشَهَادَتِهِ قَبْلَ أَنْ يُسْأَلَهَا " .