Ellicott's Commentary for English Readers - Genesis 18:21
(21) I will go down.—God examines before He punishes (see Note on Genesis 11:5) with the same care and personal inspection as the most conscientious earthly judge.Altogether.—Some take this word, not as an adverb, but as a noun (comp. Isaiah 10:23), and translate “I will see whether they have done according to the cry of it: (in which case there shall be for them) utter destruction.” But the ellipse is harsh; and inquiry, the knowing and not the punishing, is the prominent thought in the words... read more
Ellicott's Commentary for English Readers - Genesis 18:19
(19) For I know him, that he will.—This translation has most of the Versions in its favour, and means that Abraham’s good conduct earns for him the Divine condescension. But the Hebrew is, For I have known him in order that he may command his sons, &c. It gives God foreknowledge of the purpose for which He had called Abraham as the reason for thus revealing to him the method of the Divine justice. And this purpose was, that from Abraham should spring a nation whose institutions were to be... read more