'Lamb's' in the Bible

"While I was watching, thrones were set up, and the Ancient of Days took his seat. His attire was white like snow; the hair of his head was like lamb's wool. His throne was ablaze with fire and its wheels were all aflame.

but nothing ritually unclean will ever enter into it, nor anyone who does what is detestable or practices falsehood, but only those whose names are written in the Lamb's book of life.