“Little Children Are Holy, Being Sanctified through the Atonement of Jesus Christ”
Doctrine and Covenants 74:7
7 But little children are holy, being sanctified through the atonement of Jesus Christ; and this is what the scriptures mean.
Elder Hyrum M. Smith and Janne M. Sjödahl wrote:
“The consecration of the believing parent includes the children. They are sanctified through the Atonement of our Lord. They need no ordinance, until they arrive at the age of accountability, when they should be baptized, after proper instruction. Christians were forbidden to marry outside the Church [see 2 Cor. 6:14], but marriages contracted before conversion were not to be broken up, if the unconverted partner desired to continue the marriage relation.”
(The Doctrine and Covenants Commentary, rev. ed. [1951], 432.)