ذِكْرُ اسْتِحْبَابِ إِعْلَامِ الشَّاهِدِ الْمَشْهُودَ لَهُ مَا عِنْدَهُ مِنَ الشَّهَادَةِ إِذَا جَهِلَ عَلَيْهَا

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 اللَّهِ ﷺ قَالَ «أَلَا أُخْبِرُكُمْ بِخَيْرِ الشُّهَدَاءِ الَّذِي يَأْتِي بِشَهَادَتِهِ أَوْ يُحَدِّثُهَا قَبْلَ أَنْ يُسْأَلَهَا»