It was narrated from 'Abdullah bin 'Amr:
that the Prophet said: "When anyone of you gets a new wife, a servant, or an animal, let him take hold of the forelock and say: Allahumma inni as`aluka min khayriha wa khayri ma jubilat 'alaihi, wa 'audhu bika min sharriha wa sharri ma jubilat `alaih (O Allah, I ask You for the goodness within her and the goodness that she is inclined towards, and I seek refuge with you from the evil to which she is inclined).' "
English reference: Vol. 3, Book 9, Hadith 1918
Arabic reference: Book 9, Hadith 1993