Jesus said, "I am the True Vine..." He used familiar everyday things for His parables, and a grape vine was quite likely within sight when He first spoke these words. In winter the branches lose their leaves and the vine has to be pruned if it is to flourish again and bear fruit well. As the cut-off branches are fruitless, useless and dead away from the parent plant, so are Christians who are not abiding in Jesus Christ and thus sharing in His life.
