(18) The Offices of Commander and Qadi
كتاب الإمارة والقضاء
(4a) Chapter: Cases and Depositions - Section 1
(4) باب الأقضية والشهادات - الفصل الأول
Mishkat al-Masabih 3766 
Zaid b. Khalid reported God’s Messenger as saying, “Shall I not tell you of the best witness? He is the one who produces his deposition before he is asked for it.” Muslim transmitted it.
وَعَنْ زَيْدِ بْنِ خَالِدٍ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «أَلَا أُخْبِرُكُمْ بِخَيْرِ الشُّهَدَاءِ؟ الَّذِي يَأْتِي بشهادتِه قبلَ أنْ يسْأَلهَا» . رَوَاهُ مُسلم
 صَحِيحٌ  (الألباني)حكم :
Reference : Mishkat al-Masabih 3766
In-book reference : Book 18, Hadith 102