Even though you offer me your burnt offerings and grain offerings, I will not accept them; and the peace offerings of your fattened animals, I will not look upon them.
When ye offer me sacrifices and your gift, etc. מנחה, meneche, properly means a gift of flour, which was an addition to the sacrifice; but it is often taken generally for any kind of offering. It is indeed certain that the Prophet meant, that however much the Israelites accumulated their ritual observances, they did nothing towards appeasing God, inasmuch as they observed not the law...
Their feasts and assemblies, their songs and viols, all were abominations to Him because their hearts were not with Him. Nothing is more hateful than this hypocrisy, this pretense of respect when none exists. God will not smell what is offensive; He despises services meant to buy leave to go on sinning.
AI summary
Commenting on Amos 5:21-27
Though ye offer me burnt offerings, and your meat offerings, I will not accept them,.... The daily burnt offerings, morning and night, and others which were wholly the Lord's; and the "minchah", or bread offering, which went along with them; in which they thought to do God service, and to merit his favour; but instead of that they were unacceptable to him, being neither offered...