I'll have to look into that a bit more.
Here is what I had time to put together. Please let me know what you make of it.
Diane,
Lets look closer at Leviticus 23.
Starting in verse 4, we see the discussion starts with the Passover Ordinances.
We see that Passover starts at twilight on the 14th (verse 5.
On the 15th, the festival of unleavened bread begins (verse 6).
We see from the language in verse 7 that the 15th is a High Sabbath. This festival continues for seven day and the seventh day is also a High Sabbath.
Verses 9 - 14 describe how the First Fruits are offered on the day after the Sabbath, which is the festival of unleavened bread. (verse 11). This is not to be confused with the festival of harvest aka Pentecost (the reaping of the First fruits).
Leviticus 23:11 Jewish Bible - And he shall wave the omer before the Lord so that it will be acceptable for you; the kohen shall wave it on the day after the rest day.
Rashi Commentary:
on the day after the rest day: מִמָּחֳרַת הַשַּׁבָּת. On the day after the first holy day of Passover, [since a holy festival day is also שַׁבָָּת, rest day , in Scripture]. For if you say [that it means] the “Sabbath of Creation” [i.e., the actual Sabbath, the seventh day of the week], you would not know which one. - [Men. 66a]
(
https://www.chabad.org/library/bible_cdo/aid/9924#showrashi=true )
Verse 15 now begins the count for when Pentecost will occur which will be 50 days from the day after the first High Sabbath. Jews call this duration counting the Omer.
Pentecost is the festival when the first fruits from the harvest are brought in and is also called Shavout denoting the festival and the day commemorating the day the 10 Commandments were given.
Passover and Pentecost are tied together and the day of the week they land on floats depending on the year. What can also confuse folks is how verse 11 and 16 are related even though they are 50 days apart.
Just like the Bible views the night of the 15th as the night of the 14th when the Lamb is eaten (before the end of the day), The First Fruits start on the 16th, yet are celebrated 50 days later on Pentecost.