See Exodus 3:8.
For I will not go up in the midst of thee - The covenant on which the original promise Exodus 23:20-23 was based had been broken by the people. Yahweh now therefore declared that though His Angel should go before Moses, He would withhold His own favoring presence. The nation should be put on a level with other nations, to lose its character as the people in special covenant with Yahweh (see the note at Exodus 33:16). Thus were the people forcibly warned that His presence could prove a blessing to them only on condition of their keeping their part of the covenant Exodus 33:3. If they failed in this, His presence would be to them “a consuming fire” (Deuteronomy 4:24; compare Exodus 32:10).