Does the person who embraces Islam have to perform the prayers he missed on that day?
15-3-2014 | IslamWeb
Question:
Assalaam alaykum wa rahmatullahi wa barakaatuh. If a person converts to Islam during the day does he/she have to make up for the prayers that he/she has lost of that day? For example if a person converts to Islam when it is asr time. Do he have to make up fajr and dhuhr? Jazakallahu khayran.
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad 
is His slave and Messenger.
However, the question remains as to whether a new Muslim is obliged to perform the first prayer of the two prayers that are permissible to combine at the time of one of them. For example, if someone accepts Islam at the time of ‘Asr, is he obliged to perform the Thuhr prayer, or if he accepts Islam at the time of ‘Ishaa, is he obliged to perform the Maghrib prayer? The scholars have two different opinions regarding the obligation to perform those previous prayers; some of them said that it is obligatory to perform them, and others said that it is only obligatory to perform the present prayer.
Ibn Qudaamah 
said in his book Al-Mughni: “If a menstruating woman becomes pure, and a non-Muslim embraces Islam, and a child reaches puberty before sunset, then they should pray Thuhr and then ‘Asr, and if a child reaches puberty, and a non-Muslim embraces Islam and a menstruating woman becomes pure before dawn, then they should pray Maghrib and ‘Ishaa’. This view about a menstruating woman who becomes pure was traced back to ‘Abdur-Rahmaan ibn ‘Awf, Ibn ‘Abbaas, Taawoos, Mujaahid, An-Nakha’i, Az-Zuhri, Rabee’ah, Maalik, Al-Layth, Ash-Shaafi’i, Is-haaq, and Abu Thawr.
Imaam Ahmad said: 'All the Taabi’is are of this view, except Al-Hasan who said: She is only obliged to perform the prayer during the time of which she became pure.' This is the view of Ath-Thawri and the view of the scholars of the Hanafi School. The basis is that the time of the first prayer expired at the time when she had a sound excuse, so this prayer is not an obligation on her, in the same way that if she caught nothing from the time of the second prayer. It was also reported from Maalik that if one has time to perform five Rak’ahs in the time of the second prayer, then the first prayer becomes an obligation, because the time enough for the first Rak’ah of the five Rak’ahs is a valid time for praying the first prayer when one is excused, so it (the first prayer) is an obligation because there is time to pray do so (to pray one Rak'ah of the first prayer) just as if one had that much time from its preferred time, contrary to having less time than this.
Our evidence is what Al-Athram, Ibn Al-Munthir and others narrated with their chain of narrators on the authority of ‘Abdur-Rahmaan ibn ‘Awf and ‘Abdullah ibn ‘Abbaas that they said about a menstruating woman who becomes pure one ‘Rak’ah before the Fajr prayer: she has to pray Maghrib and ‘Ishaa', and if she becomes pure before sunset, then she has to pray Thuhr and ‘Asr altogether.
Another basis that the time of the second prayer is a time for the first prayer in situations where one is excused, so if a person who is excused [has a sound reason] catches this time (of the second prayer), he is obliged to pray the first prayer in the same manner that he is obliged to pray the second prayer.”
Allaah Knows best.