The tenth plague, the slaying of the first-born, God inflicted, saying, "I will take vengeance upon the Egyptians for having desired to destroy the nation that is My first-born. As the night divided itself for Abraham, that his enemies might be vanquished, so I will pass through Egypt in the middle of the night, and as Abraham was proved by ten temptations, so I will send ten plagues upon Egypt, the enemy of his children."
From the infliction of the first of the plagues until the passing of the last, after which the Egyptians yielded all that Moses and Aaron demanded, there elapsed a whole year, for twelve months is the term set by God for the expiation of sins. The deluge lasted one year; Job suffered one year; sinners must endure hell tortures for one year, and the judgment upon Gog at the end of time will be executed for the length of one year.