Sahih al-Bukhari 2116

Abu Abd Allah said: Al-Layth said: Abd al-Rahman ibn Khalid told me, from Ibn Shihab, from Salim ibn Abd Allah, from Abd Allah ibn Umar, may Allah be pleased with them both, who said: “I sold property of mine in al-Wadi in exchange for property belonging to the Commander of the Faithful, Uthman, in Khaybar. When we had made the sale, I turned on my heel and hurried out of his house, fearing that he might rescind the sale. The established practice was that the two parties to a sale had the option until they separated. Abd Allah said: Once the sale between us had become binding, I realized that I had put him at a disadvantage: I had led him to the land of Thamud, a journey of three nights, while he had led me to Medina, also a journey of three nights.”