Adam Clarke on Colossians 2:20

If ye be dead with Christ - See the notes on Rom 6:3, Rom 6:5 (note).

From the rudiments of the world - Ye have renounced all hope of salvation from the observance of Jewish rites and ceremonies, which were only rudiments, first elements, or the alphabet, out of which the whole science of Christianity was composed. We have often seen that the world and this world signify the Jewish dispensation, or the rites, ceremonies, and services performed under it.

Why, as though living in the world - Why, as if ye were still under the same dispensation from which you have been already freed, are ye subject to its ordinances, performing them as if expecting salvation from this performance?