Musnad Ahmad 35:14

'Affan narrated to us, Hammam narrated to us, Qatadah narrated to us, from Abu al-Khalil, from 'Abdullah ibn al-Harith, from Hakim ibn Hizam: That the Messenger of Allah (peace and blessings of Allah be upon him) said: "The two parties to a transaction have the option [to rescind or confirm] as long as they have not separated." He said: I found in my book: "The option [is for] three times. If they are truthful and disclose, then perhaps they will profit in their transaction; and if they lie and conceal, the blessing of their transaction will be wiped out."