Even unto the morrow after the seventh sabbath
Or weeks, forty nine days being counted, the following was the fiftieth day, or Pentecost:
shall ye number fifty days;
from whence this feast had the name of Pentecost, ( Acts 2:1 ) ; all in Israel were obliged to number those days, except women and servants F20: the manner of doing it was this F21; on the night of the second (day of the passover), after the evening prayer, they began to number; but if anyone forgot to number at the beginning of the night, he went and numbered all the night; for the commandment is for everyone to number by himself, and he ought to number standing, and to bless first, and number the days and weeks: How? on the first day he says, This is one day, until he comes to seven days, and then he says, This is the seventh day, which is one week; and on the eighth day he says, This is the eighth day, which is one week and one day, and so till he comes to the fourteenth; then he says, This is the fourteenth day, which make two weeks; and in this way he numbers, and goes on until the forty ninth day: and ye shall offer a new meat offering unto the Lord; that is, of new corn, as the Targum of Jonathan and Jarchi explain it, and this was of wheat; for it was the offering for the wheat harvest, which was offered on the fiftieth day from the offering of the sheaf or omer of the barley harvest.
The Brenton translation of the Septuagint is in the public domain.