Jeremiah 31.33-34
Septuagint

oti auth h diaqhkh mou, hn diaqhsomai tw oikw Israhl, 
meta taV hmeraV ekeinaV, fhsi kurioV, 
didouV dwsw nomouV mou 
eiV thn dianoian autwn, 
kai epi kardiaV autwn 
grayw autouV, 
kai esomai autoiV eiV qeon, 
kai autoi esontai moi eiV laon. 
kai ou mh didaxwsin ekastoV ton polithn autou, 
kai ekastoV ton adelfon autou, legwn, gnwqi ton kurion: 
oti panteV eidhsousi me 
apo mikrou autwn ewV megalou autwn, oti ilewV esomai taiV adikiaiV autwn, kai twn amartiwn autwn ou mh mnhsqw eti

New Testament - Hebrews 10.16-17

auth h diaqhkh hn diaqhsomai proV autouV 
meta taV hmeraV ekeinaV, legei kurioV:
didouV nomouV mou 
epi kardiaV autwn
kai epi thn dianoian autwn 
epigrayw autouV,
 
 
 
 

kai twn amartiwn autwn kai twn anomiwn autwn ou mh mnhsqw eti

Septuagint

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.  And they shall not all teach every one his fellow citizen, and every one his brother, saying, Know the Lord:  for all shall know me, from the least of them to the greatest of them:  for I will be merciful to their iniquities, and their sins I will remember no more

New Testament

This is the covenant that I will make with them  After those days, saith the Lord:  I will put my laws on their heart, And upon their mind also will I write them; then saith he, And their sins and their iniquities will I remember no more

Masoretic Text

But this is the covenant that I will make with the house of Israel after those days, saith Jehovah:  I will put my law in their inward parts, and in their heart will I write it; and I will be their God, and they shall be my people.  And they shall teach no more every man his neighbor, and every man his neighbor, and every man his brother, saying, Know Jehovah; for they shall all know me, from the least of them unto the greatest of them, saith Jehovah:  for I will forgive their iniquity, and their sin I will remember no more

Comments:  The NT and the LXX agree with only minor variations, though this is a much looser quotation than in Hebrews 8.8.  The MT departs significantly in one place.  This is Jeremiah 38.33-34 in the LXX.