en_tn/col/02/17.md

a shadow of the things to come

A shadow gives only a vague idea of the shape and nature of an object. In a similar way, religious traditions such as the law of Moses can only partially show the reality of Jesus Christ. (See: rc://en/ta/man/translate/figs-metaphor)

the substance

Here this means "the reality," the thing that casts the "shadow."