What a contrast: Eli and his two sons, fat and abusing the honour of being the only priests that could serve in the most holy places of the sanctuary; Samuel just doing what he was told, serving the Lord by serving Eli, but without taking on the very poor behaviour.
The fate of Aaron’s two eldest sons would have been well known to anyone who read the Law, so it should have come as no surprise when God delivered this warning:
1 Samuel 2:30-31 … I promised that your branch of the tribe of Levi would always be my priests. But I will honor those who honor me, and I will despise those who think lightly of me. The time is coming when I will put an end to your family, so it will no longer serve as my priests.
Some time later, we don’t know how long, the final verdict was delivered through a dream to a very young Samuel:
1 Samuel 3:11-14 … I am about to do a shocking thing in Israel. I am going to carry out all my threats against Eli and his family, from beginning to end. I have warned him that judgment is coming upon his family forever, because his sons are blaspheming God and he hasn’t disciplined them. So I have vowed that the sins of Eli and his sons will never be forgiven by sacrifices or offerings.
Samuel lived a different life:
1 Samuel 3:19-4:1 As Samuel grew up, the Lord was with him, and everything Samuel said proved to be reliable. And all Israel, from Dan in the north to Beersheba in the south, knew that Samuel was confirmed as a prophet of the Lord. The Lord continued to appear at Shiloh and gave messages to Samuel there at the Tabernacle. And Samuel’s words went out to all the people of Israel.
That Bible blog 