Should I not tell you of the best witnesses? He is the one who produces his evidence before he is asked for it. (Using translation from Muslim 1719)   

أَنَّ رَسُولَ اللهِ ﷺ قَالَ «أَلَا أُخْبِرُكُمْ بِخَيْرِ الشُّهَدَاءِ الَّذِي يَأْتِي بِشَهَادَتِهِ قَبْلَ أَنْ يُسْأَلَهَا أَوْ يُخْبِرُ بِشَهَادَتِهِ قَبْلَ أَنْ يُسْأَلَهَا»