It is narrated from Ibn Abbas (may Allah be pleased with them) that he was asked about exchanging one camel for two camels, so he said: Sometimes one camel is better than two camels.
Hadith Referenceمسند الإمام الشافعي / كتاب البيوع / 1452
Hadith Takhrijاسناده صحیح اخرجه البيهقى 5/ 287 - وفى المعرفة السنن والآثار له (3357) وعبدالرزاق (14140)۔ والبخارى تعليقاً قبل الحديث (2228)۔