Because that Abraham {c} obeyed my voice, and kept my charge, my commandments, my statutes, and my laws.

(c) He commends Abraham's obedience, because Isaac should be even more ready to follow the same: for as God made this promise of his free mercy, so does the confirmation of it proceed from the same fountain.

Wesley's Notes

26:5 Abraham obeyed my voice - Do thou do so too, and the promise shall be sure to thee. A great variety of words is here used to express the Divine Will to which Abraham was obedient, my voice, my charge, my commandments, my statutes, and my laws - Which may intimate, that Abraham's obedience was universal; he obeyed the original laws of nature, the revealed laws of divine worship, particularly that of circumcision, and all the extraordinary precepts God gave him, as that of quitting his country, and that (which some think is more especially referred to) the offering up of his son, which Isaac himself had reason enough to remember. Those only shall have the benefit of God's covenant with their parents, that tread the steps of their obedience.

Matthew Henry's Concise Commentary

26:1-5 Isaac had been trained up in a believing dependence upon the Divine grant of the land of Canaan to him and his heirs; and now that there is a famine in the land, Isaac still cleaves to the covenant. The real worth of God's promises cannot be lessened to a believer by any cross providences that may befall him. If God engage to be with us, and we are where he would have us to be, nothing but our own unbelief and distrust can prevent our comfort. The obedience of Abraham to the Divine command, was evidence of that faith, whereby, as a sinner, he was justified before God, and the effect of that love whereby true faith works. God testifies that he approved this obedience, to encourage others, especially Isaac.