It is Waajib to perform Fard Prayers in their times. If one does not, without an excuse, offer them in their times he will be extremely sinful. If one delays the prayer from its time with a reason he will not be sinful Some of these reasons are such that they relieve the person from the prayer. Other reasons are such which do not relieve the person from the prayer but instead require the person to make up the prayers when he is emancipated from his excuse.
Those Excuses Which Relieve one of Prayer
The women suffering menstruation or the blood discharge from childbirth, it is not Waajib on them to make up the prayers missed because of this reason. Similarly if one loses senses or is unconscious for such a period that he misses more than five consecutive prayers, one is relieved from those prayers. But if one is in such states for less than five consecutive prayers it is Waajib to make up the prayers missed. If one is out of one's senses due to alcohol or other intoxicants it is Waajib to make up the prayers missed whilst in this state.
Making Up for the Prayers
It is Waajib to immediately make up the prayer not performed in its own time -irrespective of whether it was missed due to an excuse or not.
It is not permissible to delay the making up of missed prayer. (But) Sleep, eating, striving for a livelihood and the studying of that knowledge which is Waajib are excuses for delaying the prayer. The sin of not praying in time is not redeemed by simply making up the prayer, one must also repent. Similarly the sin of missing the prayer is not relieved solely by repentance one must make up the prayer.
It is permissible for one to occupy oneself in Nafl prayer before the making up of the missed prayers. It is better to make up missed prayers and leave out all Nafl other than the Mu'akkadah Sunnahs, Forenoon Prayer, Awaabeen Prayer, Tasbeeh Prayer and the prayer greeting the Mosque.
If one misses a prayer whilst on a journey and makes this up on the return to his residence, he will only perform two Rak'ahs because he missed a prayer in which he only had to perform two Rak'ahs. If somebody misses a prayer whilst he was resider and attempts to make this up whilst on a journey he must perform all four Rak'ahs because, as before, he has missed a prayer in which he had to offer four Rak'ahs.
The maintenance of order whilst making up prayers
It is vital to maintain the order between missed prayers and the prayers of that particular time. It is not permissible to offer the prayer of that time before one has made up the missed prayer. Thus it is not pennissible to make up Zuhr Prayer before one has made up the missed Fajr Prayer. It is also vital to maintain the order between Fard and Witr prayer. Thus if one misses Witr prayer it is not permissible to perform Fajr before one has made up the missed Witr Prayer -just as one must first perform Isha Prayer before offering Witr. The importance of maintaining the order is only when one has only missed less than six prayers (excluding Witr). If one has missed less than six prayers it is vital to make up the prayers in order, perform Fajr before Zuhr, and Zuhr before Asr and so on. The proof of the necessity of maintaining an order in making up the prayers is found during the Battle of the Trench (Ahzaab) when the Prophet $ missed four prayers. The Prophet $ made up these prayers and stated, "Pray like you have seen me praying". On the day of the Trench the Prophet $ made up four prayers. These were the prayers of Zuhr, Asr, Maghrib and Isha. The Prophet $ made up these prayers after the passing of the night. He $ ordered Bilaal (ra) to say the Azaan and then he said the Iqaamah and the Prophet (pbuh) performed Zuhr, then Iqaamah was said and the Prophet $ performed Asr, then Iqaamah was said and the Prophet $ performed Maghrib and then Isha was performed.
The commandment of making up prayers in an order is made void due to the following:
1. Without counting Witr, if one's missed prayers amount to six. Witr does not make the commandment of order void even though one must maintain the order of Witr when making up prayers.
2. Time is so tight that it is impossible to offer both the missed and the prayer of the time.
3. One forgets about the missed prayer at the time of praying.
The person who has missed numerous prayers such that he does not know how many prayers he has missed it is Waajib upon him to continue making up prayers until he himself is content that he has made up the missed prayers. It is necessary that when performing the person determines the time of the Prayer. For example he can say 'I am making up the first Zuhr Prayer which I missed', or he could say 'I am making up the last Zuhr Prayer which I have missed'. It is also permissible to leave out the words first and last from the Niyyah and just say 'I am making up the Zuhr Prayer which I have missed'.
There are three time-periods when it is not permissible to make up missed prayers; When the sun is rising, at the sun's zenith and when the sun is setting and excluding these time periods it is permissible even after Asr and Fajr Prayer.