The Messenger of Allah ﷺ used to combine two prayers while traveling, Maghrib with Isha, and Dhuhr with Asr.
كان رسول الله ﷺ يجمع بين الصلاتين السفر: المغرب والعشاء، والظهر والعصر.
Ahmad (1874) narrated it from Muhammad bin Fudayl, from Yazid, from Ataa (that is, Ibn Abu Rabah), from Ibn Abbas, who said what has been mentioned. Yazid here is Ibn Abu Ziyad Hashimi, who is daif, but the hadith has other chains that strengthen it, among them what Imam Ahmad (3288) narrated from Yazid bin Harun, from Hajjaj, from Hakam, from Ibn Abbas, with similar wording. Hajjaj bin Artah Nakhai is a mudallis and he narrated with "ann" (an ambiguous form of transmission).Among them also is what Imam Ahmad likewise narrated (3397) from Ismail bin Ulaya, who said, Layth informed us, from Tawus, from Ibn Abbas, with the same wording, except that he said, "while traveling and while settled." Layth here is Ibn Abu Salim, about whom there is criticism.Among them also is what Bukhari narrated in the chapter on shortening the prayer (1107) as a suspended (mu'allaq) report, saying, Ibrahim bin Tahman said, from Husayn Muallim, from Yahya bin Abu Kathir, from Ikrima, from Ibn Abbas, with similar wording.These different routes strengthen one another, and through them the hadith rises to the level of hasan, especially since the hadith has well-established foundations.As for what was narrated from Abbas, who said, "Shall I not tell you about the prayer of the Messenger of Allah ﷺ while traveling?" He said, "We said, 'Yes indeed.'" He said, "When the sun had passed its zenith while he was still at his stopping place, he would combine Dhuhr and Asr before mounting his ride. If it had not yet passed its zenith while he was at his stopping place, he would travel on, and when the time for Asr came, he would dismount and combine Dhuhr and Asr. When the time for Maghrib came while he was at his stopping place, he would combine it with Isha. If it had not yet come while he was at his stopping place, he would mount and travel on, and when the time for Isha came, he would dismount and combine the two." This is daif.Imam Ahmad (3480) narrated it from Abdul-Razzaq, and it is also in his Musannaf (4405), where he said, Ibn Jurayj informed us, saying, Husayn bin Abdullah bin Ubaydullah bin Abbas informed me, from Ikrima and from Kurayb, that Ibn Abbas said what has been mentioned.Daraqutni (1/388) and Bayhaqi (3/163) and others also narrated it through the route of Husayn bin Abdullah, though there is disagreement over it, and Daraqutni gathered in his Sunan the various points of disagreement. However, its defect is Husayn bin Abdullah Hashimi Madani, who is daif. Ibn Main and Abu Hatim declared him daif, Nasai said he is discarded (matruk), and Juzjani said, "His hadith should not be occupied with."Nevertheless, Bayhaqi said, "It is strengthened by the corroborating evidence mentioned earlier." For more, see Talkhis Habir (2/48) and Minna Kubra (2/150).