From a blue scrap of paper on which I scribbled something in red ink, which then went through the wash, and was found finally by yours truly in the dryer:
[illegible] last part of sacrifice — water washes away the blood from the altar’s side, a sign of the erasing of the sin.
Hmm. The reference is the part that is illegible! Now I don’t remember where the washing away of the blood from the altar was described. I don’t think it’s Biblical. A search doesn’t reveal it. Maybe in the Septuagint? It was more likely a chance encounter in the either the Mishnah, Tosefta, or Babylonian Talmud. Or maybe somewhere else. (Sigh.)
I really have to remember to check all my pockets before doing the wash. That’s disappointing.