Some words from John Woodhouse on 1 Samuel 3:12-13
12 On that day I will fulfill against Eli all that I have spoken concerning his house, from beginning to end. 13 And I declare to him that I am about to punish his house forever, for the iniquity that he knew, because his sons were blaspheming God, and he did not restrain them.
The judgment of God against human wickedness is always a terrible thing to contemplate. It is hardly possible for us, embrolied as we are in the sinfulness of humanity, to see clearly the rightness of God's ways. It is very important for us to take care here and humbly listen to the word of God, not passing judgment on it, but allowing it to illumine our minds.
By the standards that we might apply to ourselves, Eli was not an excessively wicked man. [...] The trouble with all of this is that Eli is not being judged by us. It is the Lord who said that his sons were blaspheming and that he did not do what he should have done. It is not for us to sit in judgment over the Lord. He is the God of knowledge, by whom deeds are weighed (1 Sam 2:3). There is a certain absurdity in responding to this passage as though we know more about Eli's innocence (from the few pages that we have!) - and have a keener sense of justice - than the Lord does!