John Calvin 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)

While it is said, etc. He suggests that the reason for making progress never ceases as long as we live, because God calls us daily. For since faith responds to the preaching of the Gospel, as preaching continues throughout the whole course of our lives, so we ought to continue growing in faith. The phrase, then, while it is said, means the same as if he had said, “Since God never ceases to speak, it is not enough for us to readily receive His doctrine, unless we show the same teachableness and obedience tomorrow and every day that follows.”