Poole on 1 Samuel 3:18: Samuel's First Oracle...Against the House of Eli! (Part 6)
Verse 18: And Samuel told him every whit (Heb. all the things, or, words), and hid nothing from him. And he said, (Job 1:21; 2:10; Ps. 39:9; Is. 39:8) It is the LORD: let him do what seemeth him good.
[It is the Lord; what is good in His eyes let Him do] Some take this in a negative way. That is to say, Let the Lord do what is good in His eyes; but I am not able to inflict grief upon my sons: thus Saint Ephrem, Gregory, and Rupertus (Lapide). But many others more rightly take this in a positive way (thus Mendoza out of Theodoret and Procopius, Lapide, Sanchez). The response is worthy of a Priest and religious man; he submits himself and his own to God, and bears all things from Him patiently (Sanchez). In offering himself to punishment, he confesses fault. You will say, He did not emend his fault by chastising his sons (Mendoza). Response: He was not able, because he was old and debilitated (Lyra), and more fearful than worthy to be feared; and his sons were now unbridled; and the time to make corrections before death was slight. Eli attributed both goodness and power to God as avenger; and hence he professes his obedience (Mendoza). He expresses great patience, and great concord with the divine will (Mendoza’s Annotations 6 at the beginning). He did not expostulate with God, but humbly agreed (Mendoza’s Annotations 6:2). The aged man modestly bore to be reproved by a youth (Mendoza’s Annotations 6:3). The Fathers think that these words of the aged man pertain to true conversion and repentance. Indeed, this is probable, but not necessary. This is a clear confession of the divine power and righteousness. The impious are wont to excuse their sins, and, as often as they do, to accuse God (Martyr).
It is the LORD, etc.:This severe sentence is from the sovereign Lord of the world, who hath an absolute power and right to dispose of me and all his creatures as he pleaseth, to whose good pleasure I therefore freely submit: from Israel’s God, who was known by this name of Jehovah, who is in a special manner the ruler of the people of Israel, to whom it properly belongs to punish all mine offences, whose chastisement I therefore accept.
 Hebrew: וַיַּגֶּד־ל֤וֹ שְׁמוּאֵל֙ אֶת־כָּל־הַדְּבָרִ֔ים וְלֹ֥א כִחֵ֖ד מִמֶּ֑נּוּ וַיֹּאמַ֕ר יְהוָ֣ה ה֔וּא הַטּ֥וֹב בְּעֵינָ֖ו יַעֲשֶֽׂה׃  Hebrew: אֶת־כָּל־הַדְּבָרִים.  Ephrem the Syrian (c. 306-373) was a deacon and teacher, and prolific author, composing hymns, and works of theology and exegesis, in the Syriac language. He was held in universal esteem in the Church, but he is reckoned by many as the most significant of the Syriac-speaking Fathers.