It is narrated from Sayyiduna Zaid bin Aslam (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "When any of you marries a woman or buys a slave-girl, he should take hold of her forehead and pray for blessing, and when he buys a camel, he should place his hand on its hump and seek refuge from the accursed devil."