Is it permissible for a person to make a comprehensive intention for a specific thing for the rest of their life, such as intending to eat lawful food in order to strengthen themselves for the worship of Allah, and thereby gain reward?

Al-Bukhari and Muslim narrated from Umar ibn al-Khattab, may Allah be pleased with him, that the Messenger of Allah, peace and blessings be upon him, said: "Actions are but by intentions, and every man shall have but that which he intended." Therefore, knowledge and intention are inseparable; neither a mere intention without action nor a mere action without intention suffices.

Permissible matters are not rewarded unless their doer intends by them closeness to Allah Almighty. Intention distinguishes acts of worship from customs and distinguishes the ranks of acts of worship from one another.

Sheikh Taj al-Din al-Subki says: "Intention is for distinguishing acts of worship from customs, and for distinguishing the ranks of acts of worship from one another." Ibn Rajab al-Hanbali says: "Intention in the words of scholars has two meanings: One is to distinguish acts of worship from each other... or to distinguish acts of worship from customs... And the second meaning is to distinguish the purpose of the action, and whether it is for Allah alone, without partner, or for other than Him, or for Allah and others."

It is a condition for intention in acts of worship that it accompanies the beginning of the action, because an intention before the time of commencing the action is merely a resolve to do an action in the future, and that resolve may be broken, or the intention may fail, or the action may fail. Thus, none of that attains the status of worship until it is performed with the intention of seeking closeness to Allah Almighty at the time of its performance. If the action is devoid of this intention at its commencement, it does not become an act of worship, but rather it is among the permissible matters, customs, and the like.

Al-Izz ibn Abd al-Salam said: "If the purpose of intentions is to distinguish... it is obligatory that the intention accompany the beginning of the worship, so that its beginning is distinguished, and then what follows is built upon it." Sheikh Ibn Baz was asked: Is it permissible for a Muslim to have one intention for all actions? He replied: "Every action has its own intention, and a general intention is not sufficient."