For I know him
Not only by his omniscience, but with a special knowledge, such as is accompanied with peculiar love and affection; and so Jarchi says, it is expressive of love. God loved Abraham, he was a peculiar favourite of his, and therefore he would reveal his secrets to him, see ( Amos 3:2 Amos 3:7 ) ; and he knew not only who he was, but what he was, a holy good man, made so by his own grace, and what he would do by the assistance of that grace, and particularly what follows: that he will command his children, and his household after him;
to serve and worship the Lord: not his own children only, but his servants also, all in his family; lay his injunctions on them, use his authority with them, give them all needful instructions, and take such methods with them as would tend to propagate and preserve the true religion after his death: and they shall keep the way of the Lord;
which he has prescribed to men, and directed them to walk in, even everything respecting instituted worship then revealed, and particularly, to do justice and judgment;
to attend to all the laws, statutes, and judgments of God; to do that which is just and right between man and man; not as a justifying righteousness, by which Abraham himself was not justified before God; but to show their regard to the will of God, in gratitude for favours received from him, and to glorify him, as well as for the good of their fellow creatures: that the Lord may bring upon Abraham that which he hath spoken of him:
not only on Abraham personally, but upon his posterity, they walking in the ways of the Lord, according to his command and direction: the word "that" here rather signifies, as Vatablus rightly observes, the consequence than the cause, what would follow upon these things, rather than as procured by them; these being the way in which God designed to bestow them, though not for them.
The Brenton translation of the Septuagint is in the public domain.