Idris al-Awdi (may Allah have mercy on him) said that Sa'id bin Abi Burdah (may Allah have mercy on him) brought out a letter and said: This letter is from Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) to Sayyiduna Abu Musa (may Allah be pleased with him): After praise and glorification! Let not a judgement you made yesterday prevent you; you have returned to the truth, and the truth alone is ancient. Nothing nullifies the truth, and returning to the truth is better than persisting in falsehood.
(b) In the narration of Ahmad bin Hanbal (may Allah have mercy on him) and others from Sufyan it says: Let not a judgement you made yesterday prevent you, in which you consulted your own heart and were guided to what is right; the truth is ancient, nothing nullifies the truth, and returning to the truth is better than going on in falsehood.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب آداب القاضي / 20372