Here’s the best answer to its origins I could find;
The saying “cleanliness is next to godliness” does not appear in the Bible. The expression is an archaic proverb found in Babylonian and Hebrew religious tracts. Its debut in the English language, in a modified form, is found in the writings of philosopher and scientist Sir Francis Bacon. In
Advancement of Learning (1605) he wrote, “Cleanness of body was ever deemed to proceed from a due reverence to God.” Almost two hundred years later (1791), John Wesley made a reference to the expression in one of his sermons in the form we use it today. Wesley wrote, “Slovenliness is no part of religion. Cleanliness is indeed next to Godliness."
It’s hard to say where the idea of a connection between cleanliness and godliness originated. The Israelites were certainly concerned about the concepts of “clean” and “unclean” because a major portion of the Mosaic Law outlines the principles of each. Among the unclean things that God’s people were to avoid are dead bodies and carcasses, eating certain animals, leprosy, and bodily discharges. Elaborate washing rituals were prescribed to render an unclean person clean again so that he could re-enter the community and the sanctuary of the Lord (
Numbers 19). For the Jew, keeping the ceremonial laws and regulations was considered the way to approach God. Therefore, it is no wonder that the expression has its roots in Hebrew literature.
Biblically speaking, however, outward cleanliness has no connection to godliness. Jesus made it clear that men are defiled by what is in their hearts and that godliness is not attained by what we eat or don’t eat or by how often we wash our hands (
Matthew 7:18-23). The Pharisees who questioned Jesus on His teachings failed to understand that truth. They adhered to the Old Testament requirements and ceremonies as they waited for their Messiah. But when He came and stood before them, they were blinded by their own efforts to obtain righteousness by the Law, and they denied Him. He told them, “You diligently study the Scriptures because you think that by them you possess eternal life. These are the Scriptures that testify about me, yet you refuse to come to me to have life” (
John 5:39-40). For all their attention to the details of clean and unclean, they remained far from godliness.
The Greek word translated “godliness” in the New Testament means “holiness,” without which no one will see God (
Hebrews 12:14). But it is a holiness not obtained by keeping the Law, which is impossible (
Romans 3:20;
Galatians 2:16), but by being transformed into completely new creations in Christ by the power of God (
2 Corinthians 5:17;
Ephesians 4:24). At the moment of salvation, we are made completely clean and righteous before God and only then can we share in His godliness.