A Muslim cannot be labeled a disbeliever or kafir unless he totally denies the obligation of prayer or any of the Islamic obligations. However, if a Muslim abandons prayer out of laziness, he is not considered a kafir according to the majority of Muslim scholars, but rather a sinful Muslim. It is the duty of Muslims and particularly the scholars to remind such a person of the importance of performing prayers.
Dr. Muzammil H. Siddiqi, former President of the Islamic Society of North America, states: “According to the belief of Ahl as-Sunnah wa al-Jama`ah, the believer (mu’min) is a person who accepts all that has come in the Qur’an and the authentic Sunnah, and the non-believer (kafir) is a person who denies anything that has come in the Qur’an and the authentic Sunnah. Faith requires action, but a person who commits sins and neglects the obligatory duties of Islam will not be called a kafir until he/she denies the validity of Allah’s rules. Thus, those Muslims who do not pray or fast or give Zakah, etc., are sinners. They must repent and correct themselves. But they will not be called kafir unless and until they declare that they do not believe in any of these things and do not consider them necessary and obligatory duties of Islam.”