Jonas tells Gabriel that there could be love in Chapter 16.
Jonas feels very close to Gabriel. There are several reasons for this, including the fact that they both have pale eyes, a rare trait in the community. Also, families are not usually allowed to have more than two children, so Gabriel is special. Finally, Gabriel also has the Capacity to See Beyond. This means that Jonas can give him the memories.
"Things could change, Gabe," Jonas went on. "Things could be different. I don't know how, but there must be some way for things to be different. There could be colors. …” (Ch. 16)
Jonas explains that there are many things Gabe and the other citizens of the community are missing out on, including grandparents. Jonas saw the memory of grandparents, and it changed his perspective on human relationships. He went home and asked his “parents” if they loved him. They reacted with amusement, telling him he was using outdated and imprecise, meaningless language.
Jonas was horrified and saddened by this reaction. Love was the most meaningful thing he had ever experienced, and to call it meaningless was sad. Jonas spoke to Gabe quietly when they were alone in their room.
Gabriel's breathing was even and deep. Jonas liked having him there, though he felt guilty about the secret. Each night he gave memories to Gabriel: memories of boat rides and picnics in the sun; memories of soft rainfall against windowpanes; memories of dancing barefoot on a damp lawn. (Ch. 16)
Jonas says to Gabe that there could be love. This is an important moment for Jonas. He acknowledges the shortcomings of his community, and he associates Gabe with a future that is brighter. The only way this future can be created is if Jonas helps it happen, by running away and returning the memories to the people.
When Jonas finds out that Gabe is about to be released, he leaves with the baby. He has to rescue Gabe because no one else will. Jonas has gotten attached to Gabe, and cannot allow him to be killed for the community’s misguided attempts at maintaining order.