We used to bring a flour-offering called the "omer" on the sixteenth of Nisan. The halacha, as practiced when we had a bes hamikdash, is that any grain that took root after the omer is brought one year cannot be eaten until after the omer is brought the following year.

After the bes hamikdash was destroyed, however, such grain became permitted as of the morning of the sixteenth. That's by divine deceee; Raban Yochanan ben Zakay, however, decreed that it become permitted as of the start (night) of the seventeenth, so that, when the bes hamikdash is rebuilt, no one err and eat such grain in the morning of the sixteenth, before it becomes permitted with the omer's being brought.

All the above is from the Mishna and Bavli, M'nachos 68, and the Mishna on 70. When the grain had to have taken root is actually disputed in the Bavli there: some say it had to have taken root before the omer grain was cut from the ground, on the night of the sixteenth; others, before the omer offering was brought. (Mishne Tora, Maachalos Asuros 10:4, rules according to the latter view.)

Until the bes hamikdash was destroyed, the prohibition applied to any grain that took root before the omer. What about nowadays?

  1. In the absence of a bes hamikdash, what's the divinely-decreed cutoff time for grain's taking root so it is permitted by this year's seventeenth of Nisan?
  2. If that cutoff is after the time the omer was cut from the ground (or, according to the way we rule, after the time the omer was brought), did Raban Yochanan ben Zakay make a decree pushing the cutoff earlier, for the same reason as his other decree?
  3. If not, why not? Alternatively, if he did, why isn't it mentioned in the Mishna like his other decree?
  • If the answer to 2 is "no", then I suspect the answer to 3 may be "one doesn't make a decree about rare cases, and no one plants wheat at that time of year". But my knowledge of agriculture is weak enough that I'm not sure that makes sense; and, anyway, if it does make sense, I'd still like to see a source for it.
    – msh210
    Commented Jan 24, 2018 at 21:26
  • Kitzur SA 172: תְבוּאָה שֶׁנִּזְרְעָה וְנִשְׁרְשָׁה קֹדֶם ט"ז בְּנִיסָן, הַעֹמֶר הַזֶה הִתִּירָהּ, וּמֻתֶּרֶת מִיָד לְאַחַר קְצִירָתָהּ. אֲבָל אִם לֹא נִשְׁרְשָׁה קֹדֶם שִׁשָׁה עָשָׂר בְּנִיסָן, אֲסוּרָה עַד שֶׁיָבוֹא הָעֹמֶר הַבָּא - but that leaves your other questions. Commented Jan 25, 2018 at 15:47


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