He became Muslim at the time of prayer; should he make up what came before it?
Question

                If a person becomes Muslim at the time of prayer, does he have to make up what came before it?.
Praise be to Allah.
    He does not have to make up what came before it, because 
    Allaah says (interpretation of the meaning): 

    “Say to those who have disbelieved, if they cease (from 
    disbelief), their past will be forgiven”

    [al-Anfaal 8:38]. 

    i.e., if they give up their kufr and become Muslim, then 
    Allaah will forgive them their previous sins, whether these were sins of 
    neglecting obligatory duties or doing haraam acts. But he must offer the 
    prayer at the time of which he became Muslim, if there remained enough time 
    to do one rak’ah or more, because the Prophet  (peace and blessings of 
    Allaah be upon him) said: “Whoever catches up with a rak’ah of the prayer 
    has caught up with the prayer.” 

    As for the prayers that came before, he does not have to make 
    them up, such as if he became Muslim after ‘Asr, he has to make up ‘Asr, but 
    he does not have to make up Zuhr, because the time for it had ended. End 
    quote. 

    Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him).