Genesis 12.7
Septuagint



kai wfqh kurioV tw Abram, kai eipen autw, 
tw spermati sou 
dwsw thn ghn tauthn:  kai wkodomhsen ekei Abram qusiasthrion kuriw tw ofqenti autw

New Testament - Galatians 3.16

tw de Abraam erreqhsan ai epaggeliai kai tw spermati autw.  ou legei:  kai toiV spermasin, wV epi pollwn all wV ef enoV:  kai 
tw spermati sou, 
oV estin CristoV
 

Septuagint

And the Lord appeared to Abram, and said to him, I will give this land to thy seed.  And Abram built an altar there to the Lord, who appeared to him

New Testament

Now to Abraham were the promises spoken, and to his seed.  He saith not, And to seeds, as of many; but as of one, And to thy seed, which is Christ

Masoretic Text

And Jehovah appeared unto Abram, and said, Unto thy seed will I give this land:  and there builded he an altar unto Jehovah, who appeared unto him

Comments:  The NT and the LXX agree. 

It would be interesting to learn if the Hebrew word translated “seed” is singular or plural.  If plural, then this NT passage agrees with the LXX against the sense of the MT.  The NKJV, the RSV and the NASB translate:  “To your descendants I will give this land.”  The NIV is ambiguous:  “To your offspring I will give this land.”  The weight of evidence indicates that the Hebrew text would not support Paul’s argument.