This verse opens a can of theological worms. If read in isolation you come to one conclusion. If you consider all of scripture you come to another.
In isolation this would seem to be saying that it is impossible to have a clean heart. It would seem to be emphasizing the sinfulness of man and the fallen condition of creation. It would seem that the only answer is a simple, “No one.”
But that doesn’t fit with the many places where the Bible talks about people who are righteous and upright. It ignores the promises of God. It refuses to read simple statements like,
(Acts 15:8-9 KJV) And God, which knoweth the hearts, bare them witness, giving them the Holy Ghost, even as he did unto us; And put no difference between us and them, purifying their hearts by faith.Is it possible to be pure from our sin? Yes. Is it possible to do it ourselves? No.
So? The balance is that we are totally dependent on grace, but grace can do what seems impossible to us. Relax and enjoy. Try not to let your theological system get in the way of the simple promises.