isn't growing as fast as he should, and he doesn't sleep soundly. We have him in the extra care section for supplementary nurturing, but the committee's beginning to talk about releasing him." (Ch. 1)

Jonas’s father sees potential in Gabriel. All family units consist of a boy and a girl. It is against the rules to have more children. All infants remain at the Nurturing Center for the first year of life. However, Jonas’s father manages to get Gabriel a reprieve. At first, he just brings him home at night for “something extra.” Then Jonas’s father decides that Gabe could be successful if he just had a little more time.

He had been given an unusual and special reprieve from the committee, and granted an additional year of nurturing before his Naming and Placement. Father had gone before the committee with a plea on behalf of Gabriel, who had not yet gained the weight appropriate to his days of life nor begun to sleep soundly enough at night to be placed with his family unit. (Ch. 6)

All children born in a year “age” on the same day in December. This means that some babies have been born very recently, where others are really closer to a year old.  However, the babies have to meet certain requirements before they are given to families. If they don’t, they get released instead of assigned.

Jonas’s family gets attached to Gabriel. Jonas, especially, comes to view the new child as his brother. When he learns the real meaning of release by watching his father give a lethal injection to a newborn, he is horrified. Worse still, after Gabe's year is up he learns that Gabriel still has not satisfied the community, and even his father voted to release him. Jonas takes Gabriel and flees.

The answer to this question can be found in Chapter 6 of The Giver.  Specifically, it is found on p. 42 of the paperback edition.  The basic answer is that Jonas’s father had to make a special plea in order for Gabriel to get a second year of nurturing.

In the community in which Jonas and his family live, the government controls everything.  Children are not born to families in the normal way.  Instead, they are born to “Birthmothers” who specialize in bearing children.  They are then cared for in a nursery and finally assigned to a family. 

The problem with Gabriel is that he is not growing up well enough.  Therefore, Father had to make a special plea for him to prevent him from being released.  As we see on p. 42,

Father had gone before the committee with a plea on behalf of Gabriel, who had not yet gained the weight appropriate to his days of life nor begun to sleep soundly enough at night to be placed with his family unit.

So, in order for Gabriel to get another year of nurturing, Father had to make a special plea for him.  This helps to set up one of the most important parts of the book, in which Jonas leaves the community with Gabriel to prevent Gabriel from being released.

Jonas’s father makes a request to take Gabriel home and then asks for an additional year of nurturing.

Gabriel is a baby Newchild who is not growing as fast as he should, even though he has been in the “extra care section for supplementary nurturing” (ch 1, p. 7).  This demonstrates that Jonas’s father is concerned about the baby, and that people in the community do try to save babies before they throw them out.

I may ask the committee for permission to bring him here at night, if you don't mind. You know what the night-crew Nurturers are like. I think this little guy needs something extra." (ch 1, pp. 7-8)

Gabe needs to meet strict developmental milestones or he will be released.  Jonas’s father is concerned, so he peeks at his name even though babies are not named until the Ceremony of One, because he thinks calling him by his name might “enhance his nurturing” (ch 2, p. 12).

In the community, the committee of elders makes all of the important decisions.  It is actually very rare for a Nurturer to be able to take a baby home.  This demonstrates that Jonas’s father is respected in the community.

Lowry, Lois (1993-04-26). The Giver (Newbery Medal Book). Houghton Mifflin Harcourt. Kindle Edition.

In the futuristic community described in The Giver, it was the tradition that all odd personalities contrary to the society’s norm be “released.” These included the elderly, rule-breakers, or children whose development did not meet community standards. Even after supplementary nurturing in the extra care section, Gabriel’s growth rate, as well as his sleep pattern, remained wanting. Consequently, he could not be assigned to a family unit with his peers during the Naming and Placement ceremony, leaving the committee with no choice other than one to “release.” However, due to the compassion Jonas’s father had for Gabriel, he successfully sought reprieve from the committee and earned Gabriel an additional year to undergo nurturing. He was convinced that Gabriel had potential and could fit in if given the right care.

For Gabriel to be placed under the full care of Jonas’s family, each of the family members, Lily included, was required to sign an agreement stating that they would not get attached to Gabriel. Also, they had to agree that none of them would complain after one year, when Gabriel would be assigned his family unit.

The whole family had to sign contracts saying they wouldn't grow too attached to him if he continued to stay at their house in the evenings.  They had to say that they would willingly give him up the next year when it was time for him to be given to a "real" family at the naming ceremony.  This way, they would ensure he would be nurtured, but they weren't trying to break rules by getting a third child of their own.