Some people can lie and never lose any sleep.
They can steal and do other things, and it never seems to upset them. The answer could be that they have an evil conscience. The writer of Hebrews used Old Testament symbolism to convey a New Testament truth. When the priest was ministering in the tabernacle, he had to wash his hands and his feet at the laver so he would not defile the tabernacle. You and I, when we fellowship with the Lord, must be sure that we are washed clean also, not outwardly, but inwardly.