Nadab and Abihu, the sons of Aaron, who ministered in the holy office of priesthood, partook freely of wine and, as was their usual custom, went in to minister before the Lord. The priests who burned incense before the Lord were required to use the fire of God’s kindling, which burned day and night and was never extinguished. God gave explicit directions how every part of His service should be conducted, that all connected with His sacred worship might be in accordance with His holy character. And any deviation from the express directions of God in connection with His holy service was punishable with death.
(Con 80.1)
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VC
No sacrifice would be acceptable to God which was not salted or seasoned with divine fire, which represented the communication between God and man that was opened through Jesus Christ alone. The holy fire which was to be put upon the censer was kept burning perpetually. And while the people of God were without, earnestly praying, the incense kindled by the holy fire was to arise before God mingled with their prayers. This incense was an emblem of the mediation of Christ.
(Con 80.2)
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VC