Moses
Leviticus 23:15ESV·traditional attribution

“You shall count seven full weeks from the day after the Sabbath, from the day that you brought the sheaf of the wave offering.

Matthew Henry Presbyterian @wholebiblehenry

Here is the institution of the feast of pentecost, or weeks, as it is called (Deu 16:9), because it was observed fifty days, or seven weeks, after the passover. It is also called the feast of harvest, Exo 23:16. For as the presenting of the sheaf of first-fruits was an introduction to the harvest, and gave them liberty to put in the sickle, so they...

Commenting on Leviticus 23:15-22

John Gill Reformed Baptist @doctorgill

And ye shall count unto you from the morrow after the sabbath,.... Not the seventh day sabbath in the passover week, nor the whole feast of unleavened bread, but the first day of it, which was an holy convocation, a sabbath in which no servile work was to be done, Lev 23:7; and it was from the day after this, even the sixteenth of Nisan...

Jamieson-Fausset-Brown Reformed @jfbcommentary

FEAST OF PENTECOST. (Lev 23:15-22) ye shall count unto you from the morrow after the sabbath--that is, after the first day of the passover week, which was observed as a Sabbath.

Commenting on Leviticus 23:15-22