incidental, minor lapse does not affect the intention, and his fast remains valid—unless he consciously adopts a new intention, namely to abandon that day’s fast; in such a case he must renew the intention during the night.
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Question: Must the intention to fast be made before dawn every night of Ramadan, or is one intention at the beginning of the month enough? What is the ruling on someone who articulates the intention aloud each night of Ramadan?
Answer: Intention is a condition for the validity of every act of worship, fasting included. The Prophet (peace and blessings be upon him) said, “Actions are only by intentions, and each person shall have only what he intended.” Accordingly, no act of worship is valid without an intention, and fasting is no exception. He (peace be upon him) also said, “Whoever does not determine the fast during the night has no fast.” Thus the intention for fasting is obligatory, and for the obligatory fast one must intend it during the night before dawn.
Furthermore, a fresh intention is required for each day, because every day is an independent act of worship that calls for a renewed intention as the days succeed one another, in keeping with the general principle stated in the ḥadīth: “Actions are only by intentions, and each person shall have only what he intended.” Each day of Ramadan is a separate act of worship that must be specified by its own intention; the intention made at the start of the month is not sufficient unless it is renewed each night—recalled and firmly resolved upon.