2 Corinthians 3:3

declared--The letter is written so legibly that it can be "read by all men" (Co2 3:2). Translate, "Being manifestly shown to be an Epistle of Christ"; a letter coming manifestly from Christ, and "ministered by us," that is, carried about and presented by us as its (ministering) bearers to those (the world) for whom it is intended: Christ is the Writer and the Recommender, ye are the letter recommending us. written not with ink, but with the Spirit of the living God--Paul was the ministering pen or other instrument of writing, as well as the ministering bearer and presenter of the letter. "Not with ink" stands in contrast to the letters of commendation which "some" at Corinth (Co2 3:1) used. "Ink" is also used here to include all outward materials for writing, such as the Sinaitic tables of stone were. These, however, were not written with ink, but "graven" by "the finger of God" (Exo 31:18; Exo 32:16). Christ's Epistle (His believing members converted by Paul) is better still: it is written not merely with the finger, but with the "Spirit of the living God"; it is not the "ministration of death" as the law, but of the "living Spirit" that "giveth life" (Co2 3:6-8). not in--not on tables (tablets) of stone, as the ten commandments were written (Co2 3:7). in fleshy tables of the heart--ALL the best manuscripts read, "On [your] hearts [which are] tables of flesh.

— Jamieson-Fausset-Brown Commentary (public domain)