Jehovah
And Jephthah said unto the elders of Gilead, If ye bring me home again to fight against the children of Ammon, and the LORD deliver them before me, shall I be your head? Judges 11:9–11
Before anything else happens, both sides put the agreement in Jehovah's hands: He is the one who will give the victory and the witness who holds them to their word. Latter-day Saints understand this covenant God of Israel to be the premortal Jesus Christ.
How we know: the verse itself names Him · another scripture interprets it of Him
