Bulugh al-Maram, Book 14, Hadith 1414 (English) ⓘ
Narrated Zaid bin Khaled al-Juhani (RA): The Prophet said: "Shall I not inform you who is the best witness? He is the one who produces his testimony before he is asked for it." [Reported by Muslim].
عَنْ زَيْدِ بْنِ خَالِدٍ اَلْجُهَنِيِّ - رضى الله عنه - أَنَّ اَلنَّبِيَّ - صلى الله عليه وسلم -قَالَ: { "أَلَا أُخْبِرُكُمْ بِخَيْرِ اَلشُّهَدَاءِ? اَلَّذِي يَأْتِي بِشَهَادَتِهِ قَبْلَ أَنْ يُسْأَلَهَا" } رَوَاهُ مُسْلِم ٌ 1. 1 - صحيح. رواه مسلم ( 1719 ).
also referenced under: Book 14, Hadith 18 (In-Book)