Prayer is a religious duty that has specified times. Allah says: “Verily, the prayer is enjoined on the believers at fixed hours” (An-Nisaa’: 103). So each of the five Prayers has its own time limit that should not be violated. However, this religion’s ease and practicality make it permissible to combine two Prayers—Zhuhr and `Asr together or Maghrib and `Isha’ together—under some circumstances.
Sheikh Sayyed Sabiq states in his well-known book, Fiqh Us-Sunnah: Al-Athram records in his Sunnan that Abu Salamah ibn `Abdur-Rahman said: “It is a sunnah to combine the Maghrib and `Isha’ Prayers when it is raining.” Al-Bukhari records that the Prophet (peace and blessings be upon him) combined the Maghrib and `Iisha’ Prayers on a rainy night.
A summary of the opinions of the different schools of fiqh on this point follows:
The Shafi`i School says that it is allowed for the resident to combine [but not shorten] the Zhuhr and `Asr or the Maghrib and `Isha’, praying each pair in the time of the earlier Prayer only, given that it is raining when one begins the earlier Prayer and it is still raining by the time one begins the second Prayer.
According to the Maliki School, it is allowed to combine [but not shorten] the Maghrib and `Isha’ in the mosque at the time of the Maghrib due to rain or expected rain, if there is mud and darkness along the way, or if there is a lot of mud and it prevents the people from wearing their shoes. Nevertheless, he [Malik] dislikes that the Zhuhr and `Asr should be combined due to rain.
According to the Hanbali School, it is only allowed to combine [but not shorten] the Maghrib and `Isha’ in the time of the former or the latter due to snow, ice, mud, severe cold, or rain that soaks the clothes. This concession is allowed only for one who prays with a congregation in the mosque and who comes from a distance over which he could be harmed by the rain. However, for one who prays in a congregation in his house or whose path to the mosque is covered or protected, or for one whose house is right next to the mosque, it is not allowed to combine the Prayers.
Based on the above fatwa, it is allowed to combine Prayers during rain, but we should bear in mind that in our modern age one finds it easy to go to the mosque to offer the Prayers in congregation by car except in extreme weather, or one’s house is close to the mosque, so one should offer the Prayers at their fixed times without combining them.