The five daily Prayers are prescribed upon every Muslim. However, a Muslim should be keen on offering supererogatory prayers that Prophet Muhammad (peace and blessings be upon him) regularly offered. A Muslim is highly recommended to keep on offering the supererogatory prayers recommended before and after the obligatory ones for reasons such as following the Sunnah of the Prophet (peace and blessings be upon him), bringing oneself nearer to Allah, and compensating for whatever shortages and deficiencies that take place in the performance of the obligatory prayers.
Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states; There are certain recommended prayers to be done before and after certain prescribed Prayers and they are separate from the obligatory ones: Let me list them as follow:
Two rak`ahs are recommended before the Fajr Prayer; two or four rak`ahs are recommended before Zhuhr and two after, and two are recommended before `Asr; two are recommended after Maghrib, and two are recommended before `Ishaa’ and two or four are recommended after Ishaa’. Then there are three rak`ahs of Witr Prayer to be performed after `Ishaa’: It can be done either immediately after the recommended rak`ahs mentioned above or later at night; but it should be done before Fajr time.
It is important, however, to point out that these prayers are not considered as obligatory but only highly recommended. The most important of these are the two rak`ahs before Fajr and the three rak`ahs of Witr after `Ishaa’. It is important not to skip them.