Jamieson, Fausset and Brown on Amos 2:8

8. lay themselves ... upon clothes laid to pledge--the outer garment, which Ex 22:25-27 ordered to be restored to the poor man before sunset, as being his only covering. It aggravated the crime that they lay on these clothes in an idol temple.

by every altar--They partook in a recumbent posture of their idolatrous feasts; the ancients being in the habit of reclining at full length in eating, the upper part of the body resting on the left elbow, not sitting as we do.

drink ... wine of the condemned--that is, wine bought with the money of those whom they unjustly fined.