'Lamb's' in the Bible

Then one of the seven angels who had the seven bowls filled with the seven final plagues came and spoke with me, saying, “Come here, I will show you the bride, the wife of the Lamb.”

and nothing that defiles or profanes or is unwashed will ever enter it, nor anyone who practices abominations [detestable, morally repugnant things] and lying, but only those [will be admitted] whose names have been written in the Lamb’s Book of Life.