Commentary for Berakhot 72:1
ולוקח ובלבד שלא יראנו לוקט
but he must not see the man gathering it [from the bushes].
Abraham Cohen Footnotes to the English Translation of Masechet Berakhot
He is then in doubt whether the tree is in its fruit three years. Hence, Rabina declares, Mar would be right in eating the berries as well as the buds.
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