Isaiah 27.9
Septuagint

diatouto afaireqhsetai anomia Iakwb, kai touto estin h eulogia autou, 
otan afelwmai thn amartian autou

New Testament - Romans 11.27

kai auth autoiV h  par emou diaqhkh, 

otan afelwmai taV amartiaV autwn

Septuagint

Therefore shall the iniquity of Jacob be taken away; and this is his blessing when I shall have taken away his sin

New Testament

And this is my covenant unto them, When I shall take away their sins 

Masoretic Text

Therefore by this shall the iniquity of Jacob be forgiven, and this is all the fruit of taking away his sin
 

Comments:  Brenton’s “shall have taken away” and the ASV’s “shall take away” are identical in the Greek.  Paul has made sin (amartian) plural and replaced “his sin” with “their sins.”  The MT modifies the phrase “when I shall take away.”  The NASB translates the ending with:  “And this will be the full price of the pardoning of his sin.”