It appears that the Lord has now appeared again to Abraham and Sarah. This time accompanied by 2 angels. We know that the last time He came, he told them that Sarah would bear Isaac by an appointed time the next year. She is still not pregnant at this visit, so it must have been a very short time since His last visit, no more than 3 months. Why would God come and restate this promise after He already made it plain before? I believe that it is because we need to hear things over and over. When our flesh rises up, we begin to doubt. God reinforces our faith in Him by repeating His word to us to strengthen us to continue on the path He has set for us, so we can keep the eye on the prize.