Shaykh al-Islam Ibn Taymiyah (may Allaah have mercy on him) wrote a valuable book onthis matter, entitled al-Saarim al-Maslool ‘ala Shaatim al-Rasool which every believer shouldread, especially in these times when a lot of hypocrites and heretics dare to insult the Messenger (peace and blessings of Allaah be upon him) because they see that the Muslims are careless and feel little protective jealousy towards their religion and their Prophet, and they do not implement the shar’i punishment which would deter these people and their ilk from committing this act of blatant kufr.