question #1 Sahih al-Bukhari 3901, Book 63, Hadith 126 : What is the significance of fighting for a cause in Islam, especially against those who oppose the Prophet?

Sa`d said, “O Allah! You know that there is none against whom I am eager to fight more willingly for
Your Cause than those people who disbelieved Your Apostle and drove him out (of his city). O Allah!
I think that You have ended the fight between us and them.”