Albert Barnes Commentary 1 Samuel 2:29

"Wherefore kick ye at my sacrifice and at mine offering, which I have commanded in [my] habitation, and honorest thy sons above me, to make yourselves fat with the chiefest of all the offerings of Israel my people?" — 1 Samuel 2:29 (ASV)

Why do you kick? - A well-fed beast becomes unmanageable and rebellious; it refuses the yoke and bursts its bonds (Jeremiah 5:5). In the same way, the priests, instead of being grateful for the provision made for them, became dissatisfied in their pampered pride. They wantonly broke the laws of God that regulated their share of the offerings and gave themselves over to an unbridled indulgence of their passions and greed.

You honor your sons above me - What restrained Eli from taking vigorous action to vindicate God’s honor was his unwillingness to let his sons lose the lucrative office of the priesthood. He was willing to rebuke them and was grieved by their misdeeds, but he was not willing to give up the wealth and plenty that flowed into his house from the offerings of Israel.