Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: The Messenger of Allah (peace and blessings be upon him) said: "The beginning of this affair (the religion) is prophethood and mercy; then there will be caliphate and mercy; then there will be kingship and mercy; then there will be rulership (imarah) and mercy; then people will bite at one another over it as donkeys bite one another. So hold fast to jihad, and indeed the best of your jihad is ribat (guarding the frontiers), and the best of your ribat is Asqalan."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11092