Psa 51:1 To the choirmaster. A Psalm of David, when Nathan the prophet came to him, after he had gone in to Bathsheba. Have mercy on me, O God, according to thy steadfast love; according to thy abundant mercy blot out my transgressions. Psa 51:2 Wash me thoroughly from my iniquity, and cleanse me from my sin! Psa 51:3 For I know my transgressions, and my sin is ever before me. Psa 51:4 Against thee, thee only, have I sinned, and done that which is evil in thy sight, so that thou art justified in thy sentence and blameless in thy judgment. Psa 51:5 Behold, I was brought forth in iniquity, and in sin did my mother conceive me.
In addition to thinking the only difference between Protestants and Catholics was the Pope, I'd never once imagined that not all agreed on the concept of original sin. Of course, it occurred to me shortly thereafter that I can't explain our concept of it very well, so this is not a post attempting to do that. Reading the Psalms with commentary, I was able to find out that this particular verse is one of the reasons we think as we do. I never knew so many interesting things were in the Pslams!
I also discovered it is one of the "seven penitential Psalms." Just in case you were wanting to pray and be sorry (which we probably all should more frequently than we'd admit), you can find the whole list here.