“Abraham said to his servant, the oldest of his household, who had charge of all that he owned, “Please place your hand under my thigh, and I will make you swear by the LORD, the God of heaven and the God of earth, that you shall not take a wife for my son from the daughters of the Canaanites, among whom I live, but you will go to my country and to my relatives, and take a wife for my son Isaac.”” Gen. 24:2-4
Though Abraham has lived among the Canaanites for some time now, and the land of Canaan is, in essence, the “Promised Land”, Abraham is adamant about not taking a wife for Isaac from among the Canaanites. Also, God called Abraham to leave his family and his homeland, but this is where Abraham wants Isaac’s wife to be from. Why is this?
First we must realize that the scriptures do not reveal all dealings between God and humanity to us. For example, Cain and Abel brought offerings to God long before it was prescribed, and Abraham built altars before any written instruction to do so is given. Thus we can likely infer that God has, in fact, imparted such commandments to the patriarchs even though it is not recorded.
That said, the answer as to why Abraham is so vehement about Isaac’s wife being from his own people probably lies in Deuteronomy 7:
“Furthermore, you shall not intermarry with them; you shall not give your daughters to their sons, nor shall you take their daughters for your sons. “For they will turn your sons away from following Me to serve other gods; then the anger of the LORD will be kindled against you and He will quickly destroy you.” (Deut. 7:3-4)
“For you are a holy people to the LORD your God; the LORD your God has chosen you to be a people for His own possession out of all the peoples who are on the face of the earth.” (Deut. 7:6)
Another thing to note, however, is that Abraham’s own family dabbled in false idols. Consider that Abraham’s father Terah served other Gods (see Joshua 24:4). Also we see Laban has idols of his own (Gen. 31:19). Thus, the issue of false gods cannot be the sole problem. For one, there is a difference between serving other gods and turning someone away to follow such gods once they are already following the one true God. R’ Hirsch speaks of idolatry being an intellectual condition which can be changed, whereas in the case of the Canaanites, et. al, the overall more degeneracy was too much to overcome.