In The Church of Jesus Christ of Latter-day Saints, the word sealing refers to the joining together of a man and a woman and their children for eternity. This sealing can be performed only in a temple by a man who has the priesthood, or the authority from God. According to Latter-day Saint belief, the sealing means these family relationships will endure after death if the individuals live according to the teachings of Jesus Christ. For Latter-day Saints, the family is essential to God’s plan as the most important unit both on earth and in eternity.
When a man and a woman are married in a Mormon temple, the ceremony is referred to as a sealing. When children are later born to this couple, they are considered automatically sealed to their parents. Couples who joined the Church after their marriage, or did not marry in the temple originally for other reasons, still have the opportunity to be sealed together in the temple later. Parents can have their children sealed to them at that time. These sealing ordinances can also be performed vicariously for the dead, thus binding families together across generations.
Jesus Christ Himself talked about the idea of sealing in the New Testament:
Latter-day Saints believe this same authority given to Peter was given to Joseph Smith in 1829 and passed along to the current prophet and president of the Church, Thomas S. Monson. Only the prophet can give the sealing power to other men, and relatively few men hold this authority at any given time.