His statement, “upon everyone who becomes eligible for its obligation during it,” means: by being a Muslim, adult, and of sound mind.
This issue has three cases:
The first is that a person was eligible for the obligation before dawn. He must then abstain as soon as the testimony is established during the day.
The second is that a person becomes eligible for the obligation during the day before the testimony is established—for example, if he embraces Islam, reaches puberty, or regains consciousness during the forenoon, and then the testimony is established after noon. His ruling is the same as in the first case.
The third is that a person becomes eligible for the obligation after the testimony has been established—for example, if the testimony is established during the forenoon, and he embraces Islam, reaches puberty, or regains consciousness after noon. He is not required to abstain merely because the testimony has been established; rather, he is required to do so only once he becomes eligible for the obligation.
Supplement: The author, may Allah Most High have mercy on him, has informed us that whoever becomes subject to the cause of obligation during the daytime in Ramadan—such as a disbeliever who embraces Islam, a child who reaches puberty, or an insane person who regains consciousness—must abstain and make up the fast. This is the well-known position in the school of Imam Ahmad, and it is also the view of Abu Hanifah. Its evidence and reasoning have already been mentioned.
The second view is that they are required neither to abstain nor to make up the fast. This is the second report from Ahmad.
The third view is that they must abstain but are not required to make up the fast. It is also reported from Ahmad, and it was the preferred view of Shaykh Taqi al-Din—Shaykh al-Islam Ibn Taymiyyah. It is also the school of Malik, and it is the stronger view, because they were not required to abstain at the beginning of the day due to the absence of the condition of legal responsibility, and they did what they were commanded to do when they abstained upon