问24：从《古兰经》和先知的圣训中，有哪些经文依据和圣训依据表明穆斯林必须真诚（虔诚）？
Q 24: What is the textual proof from the Glorious Qur'an and the Prophetic Sunnah that a Muslim must be sincere?
A--- 安拉，至高无上者说：{诚然，纯正的宗教只属于安拉}。（输入的《祖迈尔》章，第3节）
A--- Allah, the Almighty says: {Surely the religion (i.e. the worship and the obedience) is for Allah only}. (Az-Zumar, 3)
安拉说：{所以你们应当诚心敬拜安拉}。（祖迈尔章，2）
Allah says: {So worship Allah (Alone) by doing religious deeds sincerely for Allah's sake only}. (Az-Zumar, 2)
先知穆罕默德ﷺ说:"在复活日,最有福分获得我说情的人,是从内心真诚地说'除安拉外,别无应受崇拜者'的人。"(《布哈里圣训实录》)
Prophet Muhammad (Peace be upon him) says: "The luckiest person who will have my intercession on the Day of Resurrection will be the one who said sincerely from the bottom of his heart 'None has the right to be worshipped but Allah' ". (Sahih Bukhari)
他ﷺ又说:"真主已经禁止火狱(地狱之火)降临于那些仅为求取真主的喜悦而说'除真主外别无应受崇拜者'的人。"(布哈里和穆斯林辑录)
He (Peace be upon him) said also, "Allah has forbidden the (Hell) fire for those who say, 'None has the right to be worshipped but Allah' for Allah's sake only". (Bukhari and Muslim)
《穆斯林信仰200问》——谢赫哈菲兹·伊本·艾哈迈德·哈凯米
Reference: 200 FAQ On Muslims Belief - Shiekh Hafiz Ibn Ahmed Al Hakami