then it shall be, that whatever comes forth from the doors of my house to meet me, when I return in peace from the children of Ammon, it shall be Yahweh's, and I will offer it up for a burnt offering.
Compare Gideon’s similar response to the gift of God’s Spirit. The masculine gender of the Hebrew word translated "whatever" can apply to a person or an animal, but Jephthah was probably thinking of an animal.