Khuzayma bin Thabit reported,

He passed by the Prophet ﷺ, who had just bought a horse from an Arabi. The Arabi denied the sale, saying, "I did not sell it to you."The Prophet ﷺ said, "You did sell it to me."Khuzayma bin Thabit then passed by them and heard their exchange, so he said, "I bear witness that you sold it to him."The Prophet ﷺ said to him, "How do you know this when you were not present with us?"He replied, "We have testified to what is greater than this."So the Prophet ﷺ accepted his testimony as equal to the testimony of two men, and this remained the case until Khuzayma died.

عن خزيمة بن ثابت قال

إنه مر على النبي ﷺ وقد اشترى فرسا من أعرابي فجحده الأعرابي البيع، فقال: لم أبعك، فقال النبي ﷺ: قد بعتني، فمر عليهم خزيمة بن ثابت رضي الله عنه فسمع قولهما، فقال: أنا أشهد أنك بعت، فقال له النبي ﷺ: وما علمك بذلك ولم تشهدنا؟ فقال: قد شهدنا على ما هو أعظم من ذلك، فأجاز النبي ﷺ شهادته بشهادة رجلين حتى مات خزيمة.