Musnad Ahmad 35:12

'Affan narrated to us, Hammad ibn Salamah narrated to us, Qatadah informed us, from Abu al-Khalil, from 'Abdullah ibn al-Harith ibn Nawfal, 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. If they are truthful and disclose [the defects], their transaction will be blessed for them. And if they lie and conceal [the defects], the blessing of their transaction will be wiped out."