The Messenger of Allah ﷺ said, "Shall I not tell you about the best of witnesses? It is the one who comes forward with his testimony before being asked for it, or who gives his testimony before being asked."
حدثنا أبو نوح قراد حدثنا مالك بن أنس عن عبد الله بن أبي بكر عن أبيه عن عبد الله بن عمرو بن عثمان بن عفان عن ابن أبي عمرة الأنصاري
أن رسول الله ﷺ قال ألا أخبركم بخير الشهداء الذي يأتي بشهادته قبل أن يسألها أو يخبر بشهادته قبل أن يسألها
Its isnad is sahih. Abu Nuh Qarad is mentioned by his kunya and nickname, his name being Abdul-Rahman bin Ghazwan. He is trustworthy, and his hadith is found in Bukhari. The hadith has already appeared at 21567.