A Muslim cannot be labeled a disbeliever or kafir unless he totally denies the obligation of prayer. 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 sinner. That person should sincerely repent to Allah and be eager to perform prayers at their appointed times. It is also the duty of Muslim scholars concerned with da`wah to kindly remind him of the need to perform prayer.
Sheikh Ahmad Kutty, a Senior Lecturer and Islamic Scholar at the Islamic Institute of Toronto, Ontario, Canada, states the following: “As stated in the `Aqeedah At-Tahawiyyah, which represents the standard belief of the majority of Muslims or Ahlu-Sunnah wal-Jama’ah, a person goes out of Islam by denouncing Islam just as he enters Islam by pronouncing the kalima (also known as the shahadah: there is no god but Allah; Muhammad is the Messenger of Allah). So, he enters and exits from the same door.
Having said that, we must add that if a person denies the obligation to pray, or fast, or pay Zakah, or make Hajj, then he goes out of the fold of Islam. However, that is different from someone who simply refuses to pray out of laziness; he will be still considered a Muslim if he does not deny the obligation of prayer.”
Moreover, the prominent Muslim scholar Sheikh Yusuf Al-Qaradawi, states the following:
“Muslim scholars unanimously agree that the person who abandons prayer while totally denying its obligation is a kafir. However, they disagree regarding the one who does not perform prayer out of laziness. The majority of them consider him a fasiq (sinner), and they say that the fate of that person is left to Allah, Who will judge him according to His Will.
It is the duty of Muslims, especially those concerned with calling others to Allah, to invite the one who abandons prayer to perform it, and they should use wisdom and fair exhortation in their approach in order to wisely invite him to accept the truth. If he insists on his wrong attitude, Muslims should sever their ties with him in a bid to inform him about the sin he is committing.
In conclusion, I would like to stress that it is obligatory upon the Muslim who does not perform prayer to sincerely repent to Allah, seek His Forgiveness, and be keen to perform obligatory prayers at their appointed times.”