Jamieson, Fausset and Brown on Romans 3:24

24. justified freely--without anything done on our part to deserve.

by his grace--His free love.

through the redemption that is in Christ Jesus--a most important clause; teaching us that though justification is quite gratuitous, it is not a mere fiat of the divine will, but based on a "Redemption," that is, "the payment of a Ransom," in Christ's death. That this is the sense of the word "redemption," when applied to Christ's death, will appear clear to any impartial student of the passages where it occurs.