Isaiah 1:11 To what purpose is the multitude of your sacrifices unto me? saith the LORD: I am full of the burnt offerings of rams, and the fat of fed beasts; and I delight not in the blood of bullocks, or of lambs, or of he goats. [kjv]
1:12 When ye come to appear before me, who hath required this at your hand, to tread my courts? [kjv]
1:13 Bring no more vain oblations; incense is an abomination unto me; the new moons and sabbaths, the calling of assemblies, I cannot away with; it is iniquity, even the solemn meeting. [kjv]
1:14 Your new moons and your appointed feasts my soul hateth: they are a trouble unto me; I am weary to bear them. [kjv]
Isaiah, at the start of his writings, identifies the problem. It appears to involve compulsion by the religious establishment in required ceremonies, sacrifices, meetings, etc.
Isaiah appears to elaborate on the ideas of Amos as to the "
yoke of compulsion". Barnabas refers to these ideas in his letter.