ESV, Jeremiah 31:
Brenton Septuagint Translation:33 For this is the covenant that I will make with the house of Israel after those days, declares the LORD: I will put my law within them, and I will write it on their hearts. And I will be their God, and they shall be my people.
The Hebrew writer 'quoted' the above twice. Hebrews 8:For this is my covenant which I will make with the house of Israel; after those days, saith the Lord, I will surely put my laws into their mind, and write them on their hearts; and I will be to them a God, and they shall be to me a people.
Hebrews 10:10 For this is the covenant that I will make with the house of Israel after those days, declares the Lord: I will put my laws into their minds, and write them on their hearts, and I will be their God, and they shall be my people.
It seems to us modern readers that the author of Hebrews misquoted Jeremiah twice. Further, his two quotations were not identical. Back in those days, it was not an unusual practice. Instead of quoting verbatim, they paraphrased somewhat.16 This is the covenant that I will make with them after those days, declares the Lord: I will put my laws on their hearts, and write them on their minds.