If I said krias shema shacharis before the zman because I had to go to work, do I need to say it later after the zman before I eat?
If you said krias shema after alos hashachar you don’t need to say krias shema again at the zman, and you may eat (pursuant to the laws of eating before davening), because you were yotze the mitzvah bedi’eved.
If it was before alos, you were not yotze, and must say it first.
If the zman already passed, there is no mitzvah of krias shema and you may therefore eat (see parentheses above). Nevertheless, it is still appropriate to say krias shma to be מקבל עול מלכות שמים.
Sources:
שוע”ר סי’ נ”ח ס”ו-ח, ס”י וי”א, שעבר זמנו ובמילא פקע חיובו אבל עדיין מחוייב בתפלה. ולענין ברכת ק”ש – עיין בחי’ צ”צ ברכות ג, ג’ ובקצוה”ש סי’ י”ט סקל”ד.
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