"Killing and terrorizing innocent people and the destruction of property are not condoned by Islam. Attributing all these horrific incidents to Islam is unjust. Muslims should tell the truth and unveil falseness, and inform all people that Islam is a religion of righteousness, betterment and progress. Islam is the final revelation that Allah chose for humankind to guide it from darkness to light. Allah said: “This day, I have perfected your religion for you, completed My favor upon you, and have chosen for you Islam as your religion.”
مِنْ أَجْلِ ذَلِكَ كَتَبْنَا عَلَى بَنِي إِسْرَائِيلَ أَنَّهُ مَن قَتَلَ نَفْسًا بِغَيْرِ نَفْسٍ أَوْ فَسَادٍ فِي الأَرْضِ فَكَأَنَّمَا قَتَلَ النَّاسَ جَمِيعًا وَمَنْ أَحْيَاهَا فَكَأَنَّمَا أَحْيَا النَّاسَ جَمِيعًا وَلَقَدْ جَاءتْهُمْ رُسُلُنَا بِالبَيِّنَاتِ ثُمَّ إِنَّ كَثِيراً مِّنْهُم بَعْدَ ذَلِكَ فِي الأَرْضِ لَمُسْرِفُونَ
"Whoever kills a person [unjustly]…it is as though he has killed all mankind. And whoever saves a life, it is as though he had saved all mankind.” (Qur'an, 5:32)
Corruption on earth is considered a major sin in Islam. Allah said: “And of mankind there is he whose speech may please you in this worldly life, and he calls Allah to witness as to that which is in his heart, yet he is the most quarrelsome of the opponents. And when he turns away from you, his effort in the land is to make mischief therein and to destroy the crops and the cattle, and Allah likes not mischief. And when it is said to him ‘Fear Allah,’ he is led by arrogance to more crime. So enough for him is Hell, and worst indeed is that place to rest.”
Shaykh AbdulAziz Bin Abdullah Al-As Shaykh, the Grand Mufti of Saudi Arabia
"And there is no doubt that this act can only be undertaken by one who does not believe in Allaah or the Last Day. You will not find anyone who believes in Allaah, or the Last Day, with correct and sound faith (Imaan), performing this criminal, vile act due to which great harm and corruption has occurred. only vile souls which are filled with enmity, jealousy, evil, corruption and absence of faith in Allaah and His Messenger can perform the likes of these acts. We ask Allaah for pardon and safety."
Shaykh AbdulAziz Ibn Baaz (rahimallah) concerning the attack in Riyaadh