Hebrews 3:13

exhort one another The verb implies the mutually strengtheningintercourse of consolation and moral appeal. It is the verb from which comes the word Paraclete, i.e. the Comforter or Strengthened The literal rendering is "exhort yourselves," but this is only an idiomwhich extends reciprocity into identity, and the meaning is "exhort one another."

while it is called To day Another rendering is "so long as to-day is being proclaimed." The meaning is "while the to-day of the Psalm (τὸ σήμερον) can still be regarded as applicable," i.e. while our "day of visitation" lasts, and while we still "have the light." Luke 19:44; John 12:35-36.

be hardened See note on Hebrews 3:8. The following clause indicates that God only "hardens" the heart, in the sense that man is inevitably suffered to render his own heart callous by indulgence in sin.