one who gives the salutation thinking that it has been completed, and one who gives the salutation with certainty that it has been completed because he thinks he is performing another prayer. There is a difference between the two cases. Thus, if he gives the salutation thinking that it has been completed, this is what the author means—for example, one who gives the salutation after two units of a four-unit prayer: he completes the prayer and performs the prostration of forgetfulness.

As for one who gives the salutation on the basis that the prayer has been completed because he believes he is performing another prayer that does not exceed that number of units—for example, one who gives the salutation after two units of the Zuhr prayer on the assumption that it is the Fajr prayer—then he does not build upon what preceded. This is because he gave the salutation believing that the prayer was complete in its proper number of units and contained no deficiency. Thus, he has concluded a prayer other than the prayer he was actually performing; for this reason, its parts cannot be built upon one another.

The evidence for what the author mentioned—that if one gives the salutation thinking his prayer is complete, then remembers shortly afterward, he performs the prostration of forgetfulness—is the hadith of Abu Hurayrah: One day, the Messenger of Allah ﷺ led the Zuhr or the Asr prayer and gave the salutation after two units. He then stood, walked forward to a piece of wood at the front of the mosque, and leaned upon it as though he were angry. Among the people were eminent Companions, such as Abu Bakr and Umar, but out of awe for the Messenger of Allah ﷺ, they were too intimidated to speak to him, despite being among those closest to him. Allah had endowed the Messenger of Allah ﷺ with awe-inspiring dignity.

There was among the people a man with whom the Prophet ﷺ would joke, whom he called Dhu al-Yadayn because of the length of his arms. He said, “O Messenger of Allah, did you forget, or has the prayer been shortened?” He replied, “I have not forgotten, nor has it been shortened!” His words, “I have not forgotten,” were based on what he believed, while his words, “nor has it been shortened,” were based on the legal ruling, since the ruling remained that it was four units. There was a third possibility: that he had deliberately given the salutation after two units; but this possibility does not arise with respect to