Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) says that a man sold a saddle to someone, and he did not pay its price in cash. Then the one who had bought the saddle wanted to sell it, and the one who had sold it wanted to take it back for less than what he had sold it to him for. Sayyiduna Ibn Umar (may Allah be pleased with them both) was asked about that, and he saw no harm in it, and he said: Perhaps if he sold it to someone else, he would sell it for that price or less.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10802