It is narrated from Sayyiduna Ali (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "A people will come who will leave Islam just as an arrow passes through its prey. They will recite the Qur'an but it will not go beyond their throats. Fighting them is obligatory upon every Muslim."
Hadith Referenceمسند احمد / مسند الخلفاء الراشدين / 1346
Hadith Gradingحکم دارالسلام:صحيح لغيره، روي يوسف بن أبي اسحاق عن أبيه فأدخل بينه و بين سويد بن غفلة أبا قيس الأودي