Expositor's Bible Commentary Commentary Hebrews 3:15

"while it is said, To-day if ye shall hear his voice, Harden not your hearts, as in the provocation." — Hebrews 3:15 (ASV)

The construction is uncertain. This verse may be taken with the preceding one (cf. NIV) or with what follows. Some link the words with v.13 and regard v.14 as a parenthesis: “Exhort one another while it is called Today... while it is said....” The question is not an easy one, but it seems best to take things in order, as NIV does. The words, of course, have already been quoted (see comments on vv.7–8).