In Mormonism, proxy work refers to ordinances performed in the temple on behalf of the dead. These include baptisms, confirmations, endowments, and sealings. Latter-day Saints believe that individuals who did not receive these ordinances during mortal life can choose to accept them in the spirit world. (This is sometimes called vicarious work in older LDS materials.)
This practice is central to temple activity and reflects the LDS belief that exaltation depends on receiving specific ordinances. For that reason, temple work for the dead is viewed as an act of love and service toward ancestors and all humanity, extending the possibility of eternal family relationships.
Biblical Christianity teaches that salvation is received through faith in Christ during this life (Hebrews 9:27). The Bible gives no example or command for performing ordinances on behalf of the dead. The only truly vicarious act is Christ’s atonement itself—he bore our sins in our place and gives eternal life to all who trust in him (1 Peter 3:18).