With him - i. e. as marginal, “with God,” not (as some) with himself.
He heard the voice of one speaking - Rather, he heard the voice speaking, or conversing. The effect was as though Moses was audibly addressed by another person: how this effect was produced we are not told.
Thus was the promise of Exodus 25:20-22 fulfilled; and that as an immediate response on the part of God to the cheerful readiness with which the tribes had made their offerings, and supplied everything needful for the Holy place and its service. All being now complete as God had appointed, and the camp purified from defilements, God meets Moses the mediator of the people, not as before on the peak of Sinai far away, but in the midst of them, in the dwelling-place which He henceforth vouchsafed to tenant.