Flavius Josephus, Antiquities of the Jews
William Whiston, A.M., Ed.

[248] In the month of Xanthicus, which is by us called Nisan, and is the beginning of our year, on the fourteenth day of the lunar month, when the sun is in Aries, (for in this month it was that we were delivered from bondage under the Egyptians,) the law ordained that we should every year slay that sacrifice which I before told you we slew when we came out of Egypt, and which was called the Passover; and so we do celebrate this passover in companies, leaving nothing of what we sacrifice till the day following. The feast of unleavened bread succeeds that of the passover, and falls on the fifteenth day of the month, and continues seven days, wherein they feed on unleavened bread; on every one of which days two bulls are killed, and one ram, and seven lambs. Now these lambs are entirely burnt, besides the kid of the goats which is added to all the rest, for sins; for it is intended as a feast for the priest on every one of those days. But on the second day of unleavened bread, which is the sixteenth day of the month, they first partake of the fruits of the earth, for before that day they do not touch them. And while they suppose it proper to honor God, from whom they obtain this plentiful provision, in the first place, they offer the first-fruits of their barley, and that in the manner following: They take a handful of the ears, and dry them, then beat them small, and purge the barley from the bran; they then bring one tenth deal to the altar, to God; and, casting one handful of it upon the fire, they leave the rest for the use of the priest. And after this it is that they may publicly or privately reap their harvest. They also at this participation of the first-fruits of the earth, sacrifice a lamb, as a burnt-offering to God.