Jonas was with the Giver watching his dad in the room.
Jonas dad was at the nurturing center with the twins and had to release one of them.And the one that weighted less was the one who got released.
Jonas was with the Giver when his dad was releasing one of twins.He saw what his dad had done and he got very sad.
Jonas was sad and wanted to stay with the Giver for the night so the Giver called his parents and told them that Jonas will be staying with him to go over some rules since he's the Receiver of Memory.
Jonas was VERY sad and he was talking to the Giver of how he felt about what his dad did.So Jonas now know's whats to release someone.
Jonas didn't want to go home so the Giver called his dad and told him that Jonas was going to stay with him for extra help with the rules but that was a lie.Jonas didn't want to go home because of what his dad had done.