1 Samuel 2:18

But Samuel ministered before the Lord
The ministration of Samuel, though a child, is observed both before and after the account of the ill behaviour and wickedness of Eli's sons; partly to the shame and disgrace of them, and as serving to aggravate their sin, and make it appear the more black and heinous; and partly to his honour and reputation, that he was not corrupted and turned aside from God by their evil practices. The phrase here used is different from that in ( 1 Samuel 2:11 ) there he is said to minister before Eli, under his direction and guidance, but here before the Lord; being now engaged in higher services, and which he could perform without the assistance of Eli, as in the presence of God more immediately; it seems to have respect to him when more grown in age, stature, knowledge, and experience, though here related: yet still being "a child"; not got out of his childhood, or arrived to manhood:

girded with a linen ephod;
such as priests used to wear, but not Levites in common, nor extraordinary persons on extraordinary occasions, see ( 1 Samuel 22:18 ) ( 2 Samuel 6:14 ) . This seems to be a peculiar favour, and a special honour which Eli granted to Samuel when so very young, on account of the grace of God bestowed on him in a wonderful manner; and because brought up in the tabernacle as a holy person, and a Nazarite; and because his birth was foretold, and he asked of God, as his name signified, as Procopius Gazaeus observes.