Benefit:
The author—may Allah have mercy on him—neglected to mention intention (niyya), even though it is a prerequisite for prayer. For the sake of completeness we therefore append two magnificent hadiths that rank among the cardinal foundations and towering pillars of Islam:

On the authority of the Commander of the Believers, Abū Ḥafṣ ʿUmar b. al-Khaṭṭāb—may Allah be pleased with him—who said: I heard the Messenger of Allah ﷺ say, “Actions are judged only by intentions, and each person shall have only what he intended. So whoever’s migration was to Allah and His Messenger, his migration is indeed to Allah and His Messenger; but whoever’s migration was for some worldly gain he hoped to acquire, or for a woman he wished to marry, his migration is only to that for which he migrated.” Agreed upon (1).

Vocabulary of the ḥadith
• “Actions are judged only by intentions”: The particle innamā conveys restriction; it limits the ruling to the stated quality, affirming that actions are deemed valid exclusively through intentions. It is tantamount to saying, “No actions are accepted except with intentions,” thereby negating that ruling for anything else.
• niyya (intention): Linguistically, it means “purpose.” It appears in the singular form in most narrations. Al-Bayḍāwī held that intention is “the heart’s inclination toward what it deems conducive to a goal, whether seeking benefit or warding off harm.”
Legally, it is the firm resolve to perform acts of worship in order to draw near to Allah Most High.
• “Whoever’s migration was…”: a conditional clause.
• “Then his migration is to Allah and His Messenger”: the answer to the condition. The protasis and apodosis are identical because they are understood as: “Whoever’s migration to Allah and His Messenger is made with intention and purpose, then his migration is to Allah and His Messenger in reward and recompense.”