Harden not your hearts, as in the provocation, in the day of temptation in the wilderness:
Harden not your hearts. This here only is used of man's act: usually of God's (Romans 9:18). When man is the agent, the phrase usually is "harden his neck," or 'back' (Nehemiah 9:17).
Provocation ... temptation - Massah-meribah, margin, 'tentation ... chiding,' or 'strife' (Exodus 17:1-7). Both names refer to the one murmuring of the people against the Lord at Rephidim for want of water. The first offence is the most severely reproved, as it is apt to produce manymore. Numbers 20:1-13 and Deuteronomy 33:8 mention a second, similar, in the wilderness of Sin, near Kadesh, also called Meribah.
In the day - according to the day, of, etc.