The banana we all know and love, the Cavendish, can't reproduce because it's a hybrid of two other plant species. It has no seeds and can only reproduce with the aid of farmers, who remove and transplant part of the plant's stem in order to create more of our favorite yellow fruit.
The Christian can’t reproduce either! Doesn’t matter how much they know or how beautiful they look from the outside! Without a connection to the Vine and the work of the Holy Spirit, there is no life to pass on.