Jonas and his father were worried about Gabriel’s fretfulness at night because if the baby did not sleep through the night he would be released.
In Jonas’s world, everything is carefully controlled. Children are not born to two people who fall in love, get married, and decide to have children. Instead, the community decides how many children will be born and the same number of boys and girls are born each year. Males and female adults are matched to create family units and assigned a child at a year old. Until then, the child is raised by Nurturers who are specially trained to make sure they meet special developmental milestones. If they do not meet these milestones, they are not placed in families.
Gabriel was an exception. Jonas’s father was given special permission to take him home at night for extra nurturing because he showed promise as a strong baby during the day, but did not meet all of the benchmarks needed to be placed with a family. He was given an extra year in the nurturing center and Jonas’s family took care of him at night.
Jonas developed a special bond with Gabe because he realized Gabe was unique. They both had pale eyes, and like Jonas Gabe had the capacity to receive memories. Jonas used these to quiet him at night.
"After all this extra time I've put in with him," Father said one evening after Gabriel had been bathed and was lying, for the moment, hugging his hippo placidly in the small crib that had replaced the basket, "I hope they're not going to decide to release him." (Ch. 14)
It turns out Jonas and his father were right to worry about Gabe’s fretfulness. When Jonas sees his father release the newborn twin, killing it by lethal injection, he decides to run away from the community and end their tyranny of Sameness forever by giving them their memories forever, ending their ignorance. He has to take Gabe with him, because he finds out he is going to be released.
...Father went on, "we obviously had to make the decision. Even I voted for Gabriel's release when we had the meeting this afternoon." (Ch. 21)
This novel teaches us that being different is not a sin. Our differences are what make up our humanity, rather than detract from it. In the world of Sameness created by the community, special people like Gabe are outcast and destroyed, rather than celebrated.
Lowry, Lois (1993-04-26). The Giver (Newbery Medal Book) (p. 114). Houghton Mifflin Harcourt. Kindle Edition.