Fighting for the Cause of Allah (Jihaad)
حَدَّثَنَا عَمْرُو بْنُ عَلِيٍّ، حَدَّثَنَا يَحْيَى، حَدَّثَنَا سُفْيَانُ، قَالَ حَدَّثَنِي مَنْصُورٌ، عَنْ مُجَاهِدٍ، عَنْ طَاوُسٍ، عَنِ ابْنِ عَبَّاسٍ ـ رضى الله عنهما ـ أَنَّ النَّبِيَّ صلى الله عليه وسلم قَالَ يَوْمَ الْفَتْحِ " لاَ هِجْرَةَ بَعْدَ الْفَتْحِ وَلَكِنْ جِهَادٌ وَنِيَّةٌ، وَإِذَا اسْتُنْفِرْتُمْ فَانْفِرُوا ".Narrated Ibn `Abbas:On the day of the Conquest (of Mecca) the Prophet (ﷺ) said, "There is no emigration after the Conquest but Jihad and intentions. When you are called (by the Muslim ruler) for fighting, go forth immediately." (See Hadith No)
From Sahih al-Bukhari, whose reports the scholars accept as authentic.