Pentecost, when to start Counting
The Masoretic Text provides little clarity on when to begin the count, as the instruction to ‘count from the Sabbath’ fails to specify which Sabbath is intended. This ambiguity fuels a major debate without end between two possibilities: a) the annual holy day Sabbath, or b) the weekly Sabbath.
So we’ll look to the Septuagint and the Targum of Jonathan for some clues.
(1) From the Septuagint, Pentecost is to be counted from the morrow after the first day (Leviticus 23:11 Septuagint), but what day is the first Day?
“and he shall lift up the sheaf before the Lord, to be accepted for you. On the morrow of the first day the priest shall lift it up.” Lev 23:11 LXX
Leviticus 23:5 gives the context that this takes place in the first month, Nisan, starting on the fourteenth day with Passover and the Days of Unleavened Bread, which last seven days. The first day, the fifteenth, is to be a holy gathering. On the following day, the sixteenth, the priest is to present the wave sheaf offering.
From the day you present the sheaf of the offering, count seven full weeks, which is forty-nine days, until the day after the seventh week—the fiftieth day—which will be Pentecost.
(2) And from another testimony from the Targum, the day is the day after they ate the Pascha, or Passover, the same sixteenth
And on the fifteenth day of this month the feast of unleavened cakes to the Name of the Lord. Seven days you shall eat unleavened bread.
On the first day of the feast a holy convocation shall be to you; ye shall do no work of labour,
but offer the oblation to the Name of the Lord seven days; in the seventh day of the feast shall be a holy convocation; you shall do no work of labour.
And the Lord spake with Mosheh, saying:
Speak with the sons of Israel, and say to them: When you have entered into the land which I give you, and you reap the harvest, you shall bring the sheaf of the first fruits of your harvest unto the priest;
and he shall uplift the sheaf before the Lord to be accepted for you. After the first festal day of Pascha (or, the day after the feast-day of Pascha) Leviticus 23:7-11 Jonathan
So the clear and obvious conclusion is that Pentecost is to be counted from the annual Sabbath, the fifteenth, that is, counting from the sixteenth of Nisan.
For more about critics of the Septuagint, see Lies about the Septuagint
Joel
A Prophecy of Esau and Jacob 