The requirements of prayer in supererogatory prayers are not as strict in obligatory prayer; thus, it was made easier and considerate of the different circumstances of people. Witr is the last prayer that a Muslim performs at night after the supererogatory prayers. If a Muslim is traveling, then he is granted some concessions that make the business of travel easier for him, such as shortening the prayers, and so on. From these concessions is the permissibility to pray the Witr while riding [on his mount] without [needing] to dismount from his camel, or [any other] means of transportation. In this hadeeth, the taabi’ee, Saʿid ibn Yasaar reports that he was travelling with ʿAbdullaah ibn ʿUmar (may Allah be pleased with both of them) along the path to Makkah, and they had set out [from their place of departure] at night. However, when he became fearful that the time for the Fajr Prayer was approaching and [was] about to enter without praying Witr; he dismounted from his camel and then performed the Witr prayer. Then, ʿAbdullah ibn ʿUmar said to him: “Where have you been?” Saʿeed replied: “I feared the time of Fajr to enter; thus, I dismounted and performed the Witr prayer.” To which, ʿAbdullah replied: “Is not the Messenger of Allah ﷺ an excellent model and exemplar for you to emulate?”Saʿeed responded: “Yes, by Allah! He ﷺ is an excellent example for me [to follow].” ThenʿAbdullah related to him that the Messenger of Allah ﷺ used to perform the Witr prayer while he was traveling atop the back of his camel, setting out to wherever the camel was being led and that he would perform the opening takbir facing towards the Qiblah so that he could enter into the prayer. The validity of the prayer is not affected if the mount moved into in any direction after that. He ﷺ would motion with his head, gesturing for the movements of bowing and prostration. This was to facilitate and alleviate in matter[s] of supererogatory and voluntary prayers. As for that which is obligatory, one may not pray while he is on his mount - other than out of an excuse pertaining to an intense fear or sickness, and the like..