Vouchsafe is a verb meaning to offer something in a condescending way. You might vouchsafe to your brother the secret to your key lime pie recipe.
Because vouchsafe can mean making an offering in a gracious way, it’s sometimes used in reference to religious acts — you might vouchsafe your prayers unto God. Vouchsafe can also mean doing something in a condescending way, which makes it a word that's used in many of other contexts. For example, your fancy great aunt might vouchsafe to visit your dorm room. Vouchsafe comes from the Middle English expression “To vouch something safe on someone,” meaning you confer something in a way that's secure.