Jamieson, Fausset and Brown on 1 Corinthians 15:54

54. then--not before. Death has as yet a sting even to the believer, in that his body is to be under its power till the resurrection. But then the sting and power of death shall cease for ever.

Death is swallowed up in victory--In Hebrew of Is 25:8, from which it is quoted, "He (Jehovah) will swallow up death in victory"; that is, for ever: as "in victory" often means in Hebrew idiom (Jr 3:5; La 5:20). Christ will swallow it up so altogether victoriously that it shall never more regain its power (compare Ho 6:2; 13:14; 2Co 5:4; He 2:14, 15; Re 20:14; 21:4).