Isaiah 29.13
Septuagint

kai eipe kurioV, eggizei moi 
o laoV outoV 
en tw stomati autou, kai en 
toiV ceilesin autwn timwsi me
h de kardia autwn porrw apecei ap emou:  mathn de sebontai me, didaskonteV entalmata anqrwpwn kai didaskaliaV
 

New Testament - Matthew 15.8-9


o laoV outoV 

toiV ceilesin me tima, 
h de kardia autwn porrw apecei ap emou:  mathn de sebontai me didaskonteV didaskaliaV entalmata anqrwpwn

Mark 7.6-7
O de eipen autoiV:  kalwV eprofhteusen  HsaiaV peri umwn twn upokritwn, wV gegraptai oti outoV 
o laoV 
toiV ceilesin me tima, 
h  de kardia autwn porrw apecei ap emou:  mathn de sebontai me didaskonteV didaskaliaV entalmata anqrwpwn
Septuagint

And the Lord has said, This people draw nigh to me with their mouth, and they honour me with their lips, but their heart is far from me:  but in vain do they worship me, teaching the commandments and doctrines of men
 

New Testament

Matthew 15.8-9:  This people honoreth me with their lips; But their heart is far from me.  But in vain do they worship me, Teaching as their doctrines the precepts of men 

Mark 7.6-7:  And he said unto them, Well did Isaiah prophesy of you hypocrites, as it is written, This people honoreth me with their lips, But their heart is far from me.  But in vain do they worship me, Teaching as their doctrines the precepts of men

Masoretic Text

And the Lord said, Forasmuch as this people draw nigh unto me, and with their mouth and with their lips do honor me, but have removed their heart far from me, and their fear of me is a commandment of men which hath been taught them

Comments:  The MT does not include the notion of teaching the precepts of men for doctrines.  The NIV gives the ending of this verse as, “Their worship of me is made up only of rules taught of men.”  The NRSV has, “their worship of me is a human commandment learned by rote”.

The agreement between the Septuagint and the New Testament becomes more perfect when LXX textual variations are taken into account.  Brenton’s Septuagint is based on the Codex Vaticanus.  Codices Sinaiticus and Alexandrinus omit the phrase “with their mouth.”

On the other hand, many NT manuscripts (for instance, C, W, 0601, and the Majority) begin the quotation in Matthew’s gospel with eggizei moi o laoV outoV tw stomati autwn kai - which is nearly identical to the Septuagint.