سنن أبي داود

'Amr b. Shu'aib on his father's authority said that his grandfather (Abdullah ibn Amr ibn al-'As) reported the Prophet (ﷺ) said: If one of you marries a woman or buys a slave, he should say: "O Allah, I ask You for the good in her, and in the disposition You have given her; I take refuge in You from the evil in her, and in the disposition You have given her." When he buys a camel, he should take hold of the top of its hump and say the same kind of thing.

Abu Dawud said: Abu Sa'id added the following words in his version: He should then tale hold of her forelock and pray for blessing in the case of a woman or a slave.