Tertullian

“ Whence it is manifestly shown, that in the number of the seven days there intervened a sabbath-day. For seven days, whencesoever they may have commenced, must necessarily include within them a sabbath-day; on which day not only must the priests have worked, but the city must have been made a prey by the edge of the sword by all the people of Israel. Nor is it doubtful that they “wrought servile work,” when, in obedience to God’s precept, they drave the preys of war. ”