I love how The Book of Mormon clarifies who should be baptized, in Moroni 8. Children do not need to be baptized because they have no knowledge of sin (Moroni 8:8). Only those who know how to sin should be baptized. They need to be at an age at which they are accountable for their actions.
I also appreciate how the truth has been restored that baptism is available to everyone, especially those who have passed on without knowing of the gospel of Jesus Christ. Baptism is made possible to these people through the vicarious baptisms performed in LDS Temples, and is known as “baptism for the dead”.
The Apostle Paul talked about baptism for the dead in 1 Cor 15:29. The LDS Church is the only church which performs this ordinance, which is essential for salvation; because Jesus said that “Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God.” (John 3:5)
Jesus was the first to perform a vicarious ordinance when He atoned for our sins. He suffered for us, in place of us. In the same way, in the LDS Temples, I have performed vicarious baptisms for individuals who did not know about the gospel of Jesus Christ. What a beautiful concept! Baptism is available to everyone who needs it. In a sense, by performing these ordinances, we become saviors, just like our Savior, Jesus Christ.
Baptism for the dead is the answer to a crucial dilemma; because when someone passes on who has not known about the gospel, they are instructed about the gospel. For, it says that after Jesus was crucified, that Jesus preached to the spirits in prison (1 Peter 3:19). Who are these spirits in prison? They are those who have not heard the gospel, and they are then taught the gospel (1 Peter 4:6); and when they are taught the gospel, they find out that they need to be baptized; and only the restored gospel of Jesus Christ has the answer to their problem.