Genesis 15:9

God condescends to confirm the promise of the possession of the land by a visible sign. Abraham is directed to make the usual preparations observed in old times when two parties were about to make an important covenant or alliance: cp. Jeremiah 34:18. Certain animals and birds used in sacrifice were slain, and the bodies of the former divided in two parts: hence the expression to 'strike' or 'cut' a covenant. The two parties then passed between the parts, met in the middle, and took an oath of agreement, the position signifying that if they were false to the covenant they merited a similar fate to that of the slain animals.