The instructions contained in this passage focuses on keeping the fire going all night, a task which would have required vigilance. Generally speaking, various offerings would be offered during the day, but after the evening burnt offering there would be nothing until the next day. Without careful tending, the fire would go out.
9 “Command Aaron and his sons, saying, This is the law of the burnt offering. The burnt offering shall be on the hearth on the altar all night until the morning, and the fire of the altar shall be kept burning on it.