Isaiah 6.9
Septuagint

kai eipe, poreuqhti, kai eipon tw law toutw, 

akoh akousete, kai ou mh  sunhte
kai bleponteV bleyete, kai ou mh idhte

New Testament - Luke 8.10

o de eipen:  umin dedotai gnwnai ta musthria thV basileiaV tou qeou, toiV de loipoiV en parabolaiV,
ina bleponteV mh blepwsin
kai akouonteV  mh  suniwsin

Septuagint

And he said, Go, and say to this people, Ye shall hear indeed, but ye shall not understand; and ye shall see indeed, but ye shall not perceive

New Testament

And he said, Unto you it is given to know the mysteries of the kingdom of God:  but to the rest in parables; that seeing they may not see, and hearing they may not understand

Masoretic Text

And he said, Go, and tell this people, Hear ye indeed, but understand not; and see ye indeed, but perceive not

Comments:  This is listed in the UBS Greek New Testament as a quotation from the Septuagtint (indicating a disagreement between the NT and the MT).  It is not clear why.  The only significant difference between the Septuagint and the Hebrew is in the mood of the verbs.  Sunhte and bleyete from the Septuagint are both subjunctive, for instance, as are their counterparts suniwsin and blepwsin from the New Testament.

The NRSV translates Isaiah 6.9 as “Keep listening, but do not comprehend; keep looking, but do not understand.”

See also Mark 4.12 and John 12.40.