Jamieson, Fausset and Brown on Colossians 4:18

18. Paul's autograph salutation (so 1Co 16:21; 2Th 3:17), attesting that the preceding letter, though written by an amanuensis, is from himself.

Remember my bonds--Already in this chapter he had mentioned his "bonds" (Col 4:3), and again Col 4:10, an incentive why they should love and pray (Col 4:3) for him; and still more, that they should, in reverential obedience to his monitions in this Epistle, shrink from the false teaching herein stigmatized, remembering what a conflict (Col 2:1) he had in their behalf amidst his bonds. "When we read of his chains, we should not forget that they moved over the paper as he wrote; his [right] hand was chained to the [left hand of the] soldier who kept him" [Alford].

Grace be with you--Greek, "THE grace" which every Christian enjoys in some degree, and which flows from God in Christ by the Holy Ghost (Tit 3:15; He 13:25)