What does 1 Samuel 2:25 mean?Eli is clearly hoping his sons will understand the seriousness of their sinful actions. He hopes to see sorrow and a change of heart in his boys. He wants them to understand they could be facing dire consequences from the Lord for abusing their role as priests of Israel. Specifically, they've been taking advantage of the people for profit and for sex (1 Samuel 2:12–17, 22).
He reiterates to tells Hophni and Phinehas what they should know better than anyone: if someone sins against another person, the Lord will step in and mediate between them. The law of Moses included provisions from God meant to protect those who had harmed another and wanted to make it right. In that way, the Lord became the third party between two people to bring about resolution to conflict. As priests, Eli and his sons were meant to help enforce and carry out those provisions between people in conflict.
Yet, if someone sins directly against God, the old covenant provides no designated mediator between the sinner and the Lord. Those who sin directly to God's face, so to speak, can communicate via priests, but cannot appeal to a third party to protect them from the Lord's judgment. The priests served directly before the Lord, in His presence, as mediators between the Lord and the people. When the priests sinned in their work, they did so directly against the Lord's purpose to be connected to His people. The priests had nowhere to hide from God.
That's the immediate sense of Eli's message to his sons. In a larger sense, though, everyone who sins does so against the Lord. David recognized that in confessing his own sin (Psalm 51:4). The lack of a direct, absolute mediator between sinful humans and God was the seemingly hopeless problem for which Jesus Christ was the solution (1 Timothy 2:5–6).
Eli's sons refused to listen to their father or repent from their sin. While God is forgiving, even of sinners, there are still consequences for our actions. And, eventually, God will stop offering opportunities to change one's ways (Proverbs 29:1). This verse suggests the sons' refusal to repent was connected to the Lord's will. Perhaps God hardened their hearts against repentance as He did to Pharaoh (Exodus 4:21; 7:13; 9:34; 11:10) so He could carry out His perfect justice against their sin. Perhaps, as did Pharaoh, Phinehas and Hophni have crossed their points of no return, and it was too late to turn back. The Lord had already determined to put them to death for corrupting the priesthood and Israel's system of worship.