Hadith 41

Bulugh al-Maram

Book 7: Business Transactions
وَلِمُسْلِمٍ: { فَهُوَ بِالْخِيَارِ ثَلَاثَةَ أَيَّامٍ } 1‏ .‏
Muslim has:

"He has three days in which to decide to keep them or not."