ציטירנדיקער פּירוש אויף ישעיהו 48:17

A Midrashic approach (based on Tanchuma Shelach 14): just as a father is obligated to train his son in five aspects of successful living, i.e. to circumcise him, to teach him Torah, to redeem him from a priest if he is a firstborn, to teach him an honest trade, and to arrange for him to marry a suitable woman, so G’d provided similarly for the Jewish people (His firstborn son). He circumcised them employing Joshua as the Mohel performing the ritual as recorded in Joshua 5,2. G’d “redeemed” Israel as we know from Samuel II 7,23: “and who is like Your people Israel, a unique nation on earth whom G’d went and redeemed as His people, etc.” He taught the Israelites the Torah as He said: “you shall teach them (the words of the Torah) to your children,” [employing the fathers as the teachers. Ed.]. It is also written that G’d personally taught the Torah, as stated in Isaiah 48,17: ”I the Lord am your G’d, instructing you for your own benefit.” G'd taught the people a useful trade by teaching them the commandments, as we know from Leviticus 27,34 “These are the commandments which G’d instructed, etc.” Finally, He arranged for the people to have suitable marriage partners when he blessed them saying: “Be fruitful and multiply.”
Just like a father feeds his family, anoints them with oil and washes them (arranges for all this) so G’d does the same for Israel as we know from Ezekiel 16,9-10: “I bathed you in water, and washed the blood off you, and anointed you with oil. (verse 19) and the food which I had given you, the choice flour, the oil and the honey, which I had provided for you to eat, etc.” In Numbers 21,11 we find the Israelites addressing the well of water provided for them by G’d with the words: “spring up O well-sing to it,” Just as when the father gives properties to his children the children offer gifts to the father as symbols of their gratitude, so G’d here told the Israelites to offer certain libations to express their gratitude when they would arrive in the land of Israel.