Fiqh-us-Sunnah Volume 2, Supererogatory Prayer, Fiqh 2.118A.

Imam an-Nawawi writes in his commentary on Sahih Muslim: “The majority of the scholars are of the opinion that it is allowed for the resident to combine the prayers due to some pressing need. This is the statement of Ibn Sireen and Ashhab from the companions of Malik, and al-Khattabi records it from al-Qifal and ash-Shaf’i and from Abu Ishaq al-Maruzi, and from a number of as-hab al-ahadith, and it is the conclusion of Ibn al-Munzhir. This is supported by the statement of ibn ‘Abbas: ‘The Prophet combined his salah because he did not want to put his ummah to hardship, and not because of illness or any other reason.”‘ The hadith from Ibn ‘Abbas, mentioned previously, has been recorded by Imam Muslim who states: “The Messenger of Allah combined the zuhr and ‘asr and then the maghrib and ‘isha in Medinah without there being any danger or rain.” Ibn ‘Abbas was asked: “What did he desire by that action?” He replied: “He did not want any hardship for his ummah.” Al-Bukhari and Muslim record from him that the Prophet prayed seven rak’at and eight rak’at, i.e., the zuhr and ‘asr together and the maghrib and ‘isha together, in Medinah. Muslim also records from ‘Abdullah ibn Shaqiq that ‘Abdullah ibn ‘Abbas addressed the people one day after the ‘asr salah until well after the sun had set and the stars began to appear. The people said to him: “The prayer, the prayer.” A man from the tribe of Taim continuously repeated: “The prayer, the prayer.” Ibn ‘Abbas said: “Are you teaching me the sunnah? May you have no mother.” Then he said: “I saw the Messenger of Allah combine the zuhr and ‘asr and the maghrib and ‘isha.” ‘Abdullah ibn Shaqiq commented: “I felt some uneasiness in my heart about what he had said, so I went to Abu Hurairah to ask him about that, and he confirmed what Ibn ‘Abbas had said.”