Once in Exodus
2 verses in Exodus.
Exodus 10:17Now therefore forgive, I pray thee, my sin only this once, and intreat the LORD your God, that he may take away from me this death only.
Exodus 30:10And Aaron shall make an atonement upon the horns of it once in a year with the blood of the sin offering of atonements: once in the year shall he make atonement upon it throughout your generations: it is most holy unto the LORD.