It should be known that Prayer has a certain time in which a Muslim should offer it. Allah says, (Salah (worship) at fixed times has been enjoined on the believers) (An-Nisaa’ 4:103). Also, the Prophet (peace and blessings be upon him) warned against disregarding offering the Prayers in their due times. Therefore, it is important that we try our best to never to be slack in performing Prayers on time.
Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states: We are not allowed to pray before the appointed times. Allah says, (Salah (worship) at fixed times has been enjoined on the believers) (An-Nisaa’ 4:103). The Prophet (peace and blessings be upon him) was asked, “What is the most beloved act in the sight of Allah?” He replied, “To pray at the appointed times.” Therefore, it is important that we try our best to never to be slack in performing Prayers on time.
Having said this, however, I must point out there are certain concessions—within certain reasonable limits—that we are allowed in cases when we are experiencing hardship in keeping the time because of circumstances beyond our control. In such cases, we are allowed to combine two Prayers, although we must never make it a regular habit. For instance, if you are unable to pray Zhuhr and `Asr at their appointed times, then you may pray both of them either at the time of Zhuhr or at the time of `Asr; but you are never allowed to pray them before the time of Zhuhr. Likewise, if you are finding it hard to pray Maghrib on time, then you may postpone it with the intention of jam` (combining it) with `Isha’ before the expiry of the time of the latter. You are, however, not allowed to pray them Maghrib and `Isha’ at the time of `Asr. In case of Fajr also, you are not allowed to combine it with Zhuhr.
The above ruling is based on the evidence in the sources. We read in authentic report on the authority of Ibn `Abbas (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) “combined Zhuhr and `Asr as well as Maghrib and `Isha’ for no reason of war or rain.” When asked by someone why the Prophet (peace and blessings be upon him) had done so, Ibn `Abbas replied, “He had done so in order not to cause hardship on his Ummah (community).” In other words, he wanted to show that it is permissible for the Ummah in cases of hardship to combine these Prayers so long as it is not turned into a habit in ordinary times.