Psalm 2.7
Septuagint

diagellwn to prostagma kuriou:  kurioV eipe proV me, 
uioV mou ei su, egw shmeron gegennhka se

 

New Testament - Acts 13.33

uioV mou ei su, egw shmeron gegennhka se

Hebrews 1.5

uioV mou ei su, egw shmeron gegennhka se

Hebrews 5.5

uioV mou ei su, egw shmeron gegennhka se

Septuagint

declaring the ordinance of the Lord:  the Lord said to me, Thou art my Son, to-day have I begotten thee
 

New Testament

Acts 13.33:   Thou art my Son, this day have I begotten thee

Hebrews 1.5Thou art my Son, This day have I begotten thee 

Hebrews 5.5Thou art my Son, This day have I begotten thee

Masoretic Text 

I will tell of the decree:  Jehovah said unto me, Thou art my son; This day have I begotten thee 

Comments:  The NT, LXX and MT agree.