Commentary for Genesis 18:19

כי ידעתיו FOR I KNOW HIM — this is an expression denoting "affection", as (Ruth 2:1) "kinsman (מודע) of her husband," and (Ruth 3:2) “And is not Boaz our kinsman (מודעתנו), and (Exodus 30:17) “I have distinguished (ידעתיך) thee by name”. Still the primary meaning of these terms connected with the root ידע is really that of knowing, for whoever holds a person in affection attaches him to himself, so that he knows him well and is familiar with him. And why do I hold him dear?

FOR I HAVE KNOWN HIM (‘YEDATIV’), TO THE END (‘LEMA’AN’) THAT HE MAY COMMAND HIS CHILDREN. Rashi comments: “For I have known him, as the Targum takes it, is an expression denoting affection, just as A kinsman (‘moda’) of her husband’s;¹²⁰Ruth 2:1. And I know thee.¹²¹Exodus 33:17. Still the main connotation of all these expressions is that of knowing, for he who holds a person in affection and draws him to himself knows him well and is familiar with him. But if you explain it as the Targum does — i.e., “I know that he will command his children” — then the word lema’an (to the end) does not fit into the sense.”¹²²Our Rashi has a different text. See notes in my Hebrew commentary, p. 110. See also Note 125 further.
It is possible that the word yedativ means “I have raised him and elevated him so that he shall command his children after him to do that which is right before Me, and therefore I will make him a great and mighty nation so that he should serve Me. In a similar sense are the verses: I know thee (‘yedaticha’) by name;¹²³Exodus 33:12. The sense would thus be: “I have made thee great in name.” What is man, that Thou knowest htm?¹²⁴Psalms 144:3. The sense here then would be: “What is man before Thee that Thou hast given him greatness?” Or the verse may be stating, I know that he will command,¹²⁵Ramban thus differs with Rashi, who said that if you take the sense of the verse to be, “I know of him that he will command,” then the word lema’an does not fit the context. Ramban proceeds to show from Exodus 23:12 that the words lema’an yanuach mean she’yanuach (that he may rest); here likewise, lema’an asher yetzaveh means she’yetzaveh (that he will command). Thus, the word lema’an is seen to fit into the context. and in a similar sense is the verse, So that thine ox and thine ass may have rest (lema’an yanuach),¹²⁶Exodus 23:12. See Note above. meaning that he may have rest.
The correct interpretation appears to me to be that the word yedativ literally means “knowing.” He is thus alluding that G-d’s knowledge, which is synonymous with His Providence in the lower world, is to guard the species, and even the children of men are subject despite it to the circumstantial evil occurrences until the time of their visitation comes. But as regards His pious, He directs His Providence to know each one individually so that His watch constantly attaches to him, His knowledge and remembrance of him never departs, as it says: He withdraweth not His eyes from the righteous.¹²⁷Job 36:7. There are many verses on this theme, as it is written, Behold, the eye of the Eternal is toward them that fear Him,¹²⁸Psalms 33:18. See Moreh Nebuchim III, 51, where Rambam’s theory on Divine Providence is seen to be similar to that which Ramban expresses here. and other verses besides.

כי ידעתיו, as a symbol of righteousness.

את ביתו ואת בניו, both the members of his household who were not biologically related to his as well as his family, in order to teach us that a man is obligated to monitor the conduct of all members of his household and is responsible for their misconduct if he did not use his authority to put a stop to it. David spells out this responsibility of the head of the household in Psalms 101,6-7 when he said: עיני בנאמני ארץ לשבת עמדי הולך בדרך תמים הוא ישרתני. לא ישב בקרב ביתי עושה רמיה, “my eyes are on the trusty men of the land, to have them at my side. He who follows the way of the blameless shall be in my service.” He who deals deceitfully shall not live in my house;” Concerning the wicked Solomon says in Proverbs 29,12: “a ruler who listens to lies, all his servants become wicked.”

כי ידעתיו, “for I know him intimately.” Rashi follows Onkelos in understanding the word ידעתיו as: “I love him.” G’d is saying that the reason He loves Avraham is because he will command his family and people under his control to observe the ways of the Lord. Nachmanides understands the word ידעתיו as a description of Avraham as an individual whom G’d has endowed with greatness in order that he will pass on his lifestyle to his descendants, his lifestyle being that he emulates the ways of the Lord. It is because of this that G’d will make a great nation out of him. That nation in turn will serve the Lord just as their founder had done. Another meaning of the word ידעתיו in connection with the preface למען could be parallel to Deut. 5,14 למען ינוח עבדך ואמתך, “in order that your manservant and woman servant shall rest, (abstain from forbidden activities on the Sabbath)” In that instance the word למען substitutes for the prefix ש, i.e. שינוח. Personally, I believe that the word has to be understood as ידיעה, true knowledge of someone, like one possesses knowledge of facts. G’d hints that He supervises Avraham (and others) minutely even though we live in the world known as the עולם השפל, “the lower regions of the universe.” Although many people are assigned a role in life and are therefore exposed to what appear as accidents of nature until the day they die and hopefully qualify for residence in the higher regions of the universe, deserving individuals will always attract G’d’s attention and especial protection while on earth. Avraham will be a prime example of such people, and he can inspire them due to what people know about him.

למען אשר יצוה את בניו ואת ביתו אחריו, the dictates by the patriarchs to their respective children, all only by word of mouth, without there being a written document claiming to be G’d’s instructions such as the Torah nowadays, were observed by these children of the patriarchs as if the Torah had already been given, and as if they each had said: “I will do and I will hear.” This is further proof that the oral Torah is not subordinate to the written Torah. All of what was written in the written Torah was included in what the people heard at Mount Sinai, as well as all that G’d taught Moses while he was on that mountain. Just as there is no difference between the specific commandment the people had heard, i.e. the Ten Commandments, and the remainder of the written Torah, so there is no difference [in the authenticity and binding nature Ed.] of the commandments not spelled out in the written Torah, but handed down by the sages orally from generation to generation. (Rabbeinu Bachya)

למען אשר יצוה את בניו ואת ביתו, “in order that he will command his sons and the members of his household, etc.” He should point out to them that unless they followed their father’s or master’s tradition, they might wind up just as the people of Sodom would in short order. [Note that here as well as at the time of the deluge, G-d was not punishing these people for their paganism but for not dealing fairly with one another. Ed.]

למען אשר יצוה BECAUSE HE WILL GIVE HIS CHILDREN CHARGE CONCERNING ME TO KEEP MY WAYS. If, however, you explain it as the Targum, “I know “of” him that he will command his sons etc.”, then the word למען does not fit into the sense.

למען אשר יצוה את בניו, G’d did all of the foregoing in order that Avraham would instruct his sons to emulate the ways of G’d having personal experience of G’d’s great love for mankind, seeing how His love extended even to the wicked.

על אברהם, meaning on his descendants after him.

יצוה HE WILL COMMAND — This form of the verb (the imperfect) expresses frequentative action, as (Job 1.5) "This Job used to do" (יַעֲשֶׂה)

ושמרו...לעשות צדקה ומשפט למען הביא ה' על אברהם את אשר דבר אליו. The ultimate purpose of G’d in revealing to Avraham His manner of meting out justice was to ensure that He would have an opportunity to fulfill all the promises He had made to Avraham. [promises which were largely conditional on Avraham’s offspring being true to his teachings. Ed.] (compare 17,7)

למען הביא IN ORDER THAT [THE LORD] MAY BRING — Thus will he ever command his children saying “Keep the way of the Lord in order that the Lord may bring upon Abraham etc.” Since it does not say here ‘‘upon the house of Abraham”, but upon Abraham himself, we may infer that he who trains up a righteous son is as though he never dies (Genesis Rabbah 49:4).