There is a Jewish custom that follows the command to count the days between Passover and Pentecost, known as counting of the Omer.
““Speak to Bnei-Yisrael and tell them: When you have come into the land which I give to you, and reap its harvest, then you are to bring the omer of the firstfruits of your harvest to the kohen. He is to wave the omer before ADONAI, to be accepted for you. On the morrow after the Shabbat, the kohen is to wave it.”
Leviticus 23:10-11 TLV
““Then you are to count from the morrow after the Shabbat, from the day that you brought the omer of the wave offering, seven complete Shabbatot. Until the morrow after the seventh Shabbat you are to count fifty days, and then present a new grain offering to ADONAI.”
Leviticus 23:15-16 TLV