In the book Irshad ul Quloob a narration states that one day Hazrat Amir ul-Mu’minīn ‘Ali (a.s.) was in the midst of fighting during the battle of Siffīn. In spite of these circumstances he often glanced at the sun between the rows of fighters. Ibn Abbas asked him why he kept glancing at the sun? Imam (a.s.) said, “I am looking towards Zawāl (decline of sun from its zenith) so that I may perform Prayer.” Ibn Abbas asked him if there was opportunity to recite prayer in these trying circumstances? Imam (a.s.) replied, “Why are we fighting these people? Our aim in fighting these people itself is the establishing of Prayer.”
Ibn Abbas has related that ‘Ali (a.s.) never omitted the Midnight Prayer, not even during the battle of Siffīn when it was extreme winter.