The Messenger of Allah said: "The most virtuous fast is the fast of my brother Dawud. He would fast a day, and not fast (the next) day. He would not flee at the time of engagement (with the enemy)." (Using translation from Tirmidhī 770)
قَالَ رَسُولُ اللهِ ﷺ أَفْضَلُ الصَّوْمِ صَوْمُ أَخِي دَاوُدَ كَانَ يَصُومُ يَوْمًا وَيُفْطِرُ يَوْمًا وَلَا يَفِرُّ إِذَا لَاقَى