Before God - In the temple, where God dwelt by the symbols of His presence. The temple was regarded by the Jews as the "house" or dwelling of God; and in the "first" temple there was, in the most holy place, a "cloud" called the Shechinah, or a visible sign of the presence of God. It was thus "before God" that Zechariah offered incense.

Before God - In the temple, where God used to manifest his presence, though long before this time he had forsaken it; yet, on this important occasion, the angel of his presence had visited it.

And it came to pass, that while he executed the priest's office,.... To which he was called and ordained, even to offer gifts and sacrifices for men; whilst he was in the way of his duty, when oftentimes God appears to, and in favour of his people; whilst he was performing it,
before God; in the temple, where was the symbol of the divine presence, before the altar of the Lord; and as having the fear of God before his eyes; considering himself as in the sight of God, and doing his work faithfully and sincerely:
in the order of his course; taking his turn in the order of the course of Abia, to which he belonged; See Gill on Luke 1:5.

While he executed the priest's office. His course came on duty once in twenty-four weeks, and then he repaired to Jerusalem to remain his week.