Imam an-Nawāwī in the Commentary of the Muhaźźab said:

Al-Jam’u (Combining) between the Jum’ah (Friday Prayer) and the Aśr prayer during rain is permissible as mentioned by Ibnu Kaj, the author of al-Bayān and others. If the ‘Aśr prayer is brought forward to the Jum’ah, the occurrence of rain in the iftitāh of the two prayers and during the salām of the Jum’ah is stipulated as a necessary condition as per the other prayers. The author of al-Bayān said: The occurrence of rain is not stipulated as a condition during the two khutbahs. This is because they are not considered as the prayer, rather a condition from amongst the conditions of the Jum’ah. Therefore, rain is not a stipulated condition during the two khutbahs as how it is not stipulated as a condition during tahārah (purification). Ar-Rāfi’ī said: it has been disputed, with regard to this, in view of the opinion that the two khutbahs replaces the two raka’ahs.

The author of al-Bayān and others said if one wishes takhīr (delaying) of the Jum’ah to the time of the ‘Aśr prayer, it is permissible if we considered ta’khīr of the Zhuhr prayer to the ‘Aśr prayer permissible. He then makes khutbah in the time of the ‘Aśr prayer and then pray the Jum’ah prayer followed by the ‘Aśr prayer. The occurrence of rain in the time of ‘Aśr prayers is not a stipulated as a condition as mentioned earlier. They sought dalīl (proof) considering the fact that all the periods in which it is permissible to carry out the Zhuhr prayer as adā’ (non qadhā’) is also when it is permissible to carry out the Jum’ah prayer and the two khutbahs.