delectable things - the idols in which they take such pride and delight.
not profit - (Hab 2:18).
they are their own witnesses - contrasted with, “Ye are My witnesses” (Isa 44:8). “They,” that is, both the makers and the idols, are witnesses against themselves, for the idols palpably see and know nothing (Psa 115:4-8).
that they may be ashamed - the consequence deducible from the whole previous argument, not merely from the words immediately preceding, as in Isa 28:13; Isa 36:12. I say all this to show that they are doomed to perish with shame, which is their only fitting end.