"For I knew him, because he commands his children and his household after him, that they keep the path of Hashem... " (Bereshith 18:19)
G-d, referring to Abraham Abinu, 'a"h, uses the phrase: "I knew him", which according to Rashi, denotes affection and fondness.
We may ask, why specifically now, is G-d addressing Abraham Abinu with such an expression of love? Surely, Abraham Abinu's entire entity was about serving G-d with extreme devotion. Such an outstanding individual should have merited to receive an acknowledgment of G-d's love earlier!
Hakham Mordekhai Eliyahu, 'a"h, quotes his uncle, Hakham Yehuda Sadqa, 'a"h, Rosh Yeshibath Porath Yosef, who made the following profound statement. Abraham Abinu, 'a"h, did not merit to have G-d say about him "For I knew him" after all the inconceivable and unthinkable tests he went through. He did not hear G-d call him with an affectionate form of speech. Why? It was the fact that Abraham Abinu 'a"h commanded his children and household to follow the path of the Torah, that was the single most important act which elicited a passionate expression for him!
We learn from Abraham Abinu 'a"h, an important lesson in parenting. Our task as parents is to bring up our children in such a way that their commitment to keeping the Miswoth will be fundamental. Their passion to follow G-d's will should be ingrained in them, so that they themselves will continue in this path and pass their fear of Heaven and love of Hashem to the next generations as well.