كتاب البيوع
Read the English translation first, with the original Arabic directly underneath.
Narrated Hakim bin Hizam":
The Prophet (ﷺ) said, "The buyer and the seller have the option of canceling or confirming the deal unless they separate."
الْبَيِّعَانِ بِالْخِيَارِ مَا لَمْ يَفْتَرِقَا