Reference for Berakhot 55:14

ושל מוספין כל היום: א"ר יוחנן ונקרא פושע

The additional Tefillah [may he said] at any time in the day. [R. Judah says: Until the seventh hour.] R. Johanan said : If one reads it after the seventh hour, he is called a transgressor.

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