Prayer is an act of worship that is limited to the way it is prescribed in the religious texts. The Prophet (blessings and peace of Allah be upon him) defined its times, and explained the beginning and end of each time, and how one may catch up with the prayer before its time ends. In this hadith, the Messenger of Allah (blessings and peace of Allah be upon him) described the minimum amount of the prayer that one may do (before the time for it ends) so that he may be regarded as having caught up with the prayer, and that the one who delays doing an obligatory prayer until its time has almost ended, but he manages to catch up with even one ‘sajdah’ before its time ends, is regarded as having caught up with the prayer within its time, even if he does the remaining rak‘ahs after the time for the prayer has ended. What is meant by ‘sajdah’ (lit. prostration) here is a complete rak‘ah, with its ruku‘ (bowing) and sujud (prostration). The prayer may be called sujud (lit. prostration), just as it may also be called ruku‘ (bowing). It was also said that what is meant by sajdah in the phrase “If one of you catches up with a sajdah” is sajdah in the true sense (that is, prostration), and not an entire rak‘ah. If catching up with the prayer has to do with the ruling on the prayer, it is the same whether one catches up with a complete rak‘ah or less than that. It is sufficient to catch up with the opening takbir (takbirat al-ihram) [before the time for the prayer ends], because this is the issue of catching up with the prayer (and avoiding falling into sin by missing the prayer), therefore catching up with the rak‘ah is the same as catching up with the takbirat al-ihram. These two prayers (Fajr and ‘Asr) are singled out for mention, to the exclusion of others – even though this ruling is not specific to them; rather it includes all the prayers – because they are done at the two ends of the day, and if the worshipper has offered part of the prayer, then the sun rises or sets, he will realize that the time for the prayer has ended. So if the Prophet (blessings and peace of Allah be upon him) did not explain this ruling, the worshipper would think that he had missed the prayer and his prayer had been rendered invalid because the time had ended. Moreover, the Prophet (blessings and peace of Allah be upon him) had forbidden praying at the time of sunrise and sunset. Therefore he (blessings and peace of Allah be upon him) stated that the prayer of the one who catches up with a rak‘ah of these two prayers (before the time for them ends) is valid, lest the worshipper think that his prayer had been rendered invalid with the ending of these two times. This applies to one who has a legitimate excuse for not having offered the obligatory prayer at the beginning of its time. He may pray at the end of that time, and catch up with the prayer before sunrise and before sunset; otherwise, the best of deeds is offering prayer on time. It was said that what is meant in this hadith is that if a person is among those who are accountable and required to pray, and is able to catch up with as much as one rak‘ah of the prayer before the sun rises, then he is regarded as having caught up with it and fulfilled the obligation of praying Fajr. This applies only to those with legitimate excuses; if a menstruating woman becomes pure (and rushes to do ghusl), or an insane person recovers his sanity, or a Christian becomes Muslim, or a boy reaches puberty, if any of these people catches up with one rak‘ah then he or she has fulfilled the obligation of praying..