It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that a man came to him and said: "What do you say about al-Walid bin Uqbah, while drops of wine are dripping from his beard?" He said: "The Messenger of Allah (peace and blessings be upon him) forbade us from spying (probing to uncover faults); but if some offence becomes apparent to us (without spying), we will take him to account for it." This hadith is sahih al-isnad (its chain is authentic), but the two Shaykhs (Bukhari and Muslim) did not record it.