Hebrews 3:13

παρακαλεῖτε ἑαυτούς. The verb implies the mutually strengthening intercourse of consolation and moral appeal. It is the verb from which comes the word Paraclete, i.e. the Comforter or Strengthener. The literal rendering is “exhort yourselves,” but this is only an idiom which extends reciprocity into identity, and the meaning is “exhort one another” (ἀλλήλους). Comp. 1 Corinthians 6:7; Ephesians 4:32, &c.

ἄχρις οὖ τὸ σήμερον καλεῖται, “so long as it is called ‘To-day.’  ” It is however true that ἄχρις in the N. T. generally means “until.” 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.

σκληρυνθῇ. 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.