Leviticus 9:1

And it came to pass on the eighth day, that Moses called Aaron and his sons, and the elders of Israel;

The eighth day came after the seven days set apart for consecrating the priests, when Moses gathered Aaron together with his sons and the elders of Israel as Aaron was entering upon his priestly work. Aaron then presented the sacrifices that God had appointed and pronounced blessing upon the people. Since everything in the service had been carried out exactly as God had directed, God showed His acceptance of the offering and manifested His glory by sending fire that consumed it. The congregation understood this as a token of God's glory and favor, giving praise and worship to Him and bowing with their faces to the ground before Him.