Buraydah (may Allah be pleased with him) reported: The Messenger of Allah (may Allah’s peace and blessings be upon him) said: "The covenant between us and them is prayer; so, whoever abandons it has disbelieved."
Authentic - Narrated by At-Tirmidhi, An-Nasā’i, Ibn Mājah, Ahmad
The Prophet (may Allah's peace and blessings be upon him) pointed out that the covenant and pledge between the Muslims and the disbelievers and hypocrites is prayer. So, whoever abandons it has become a disbeliever.
Daga Cikin Fa idodin Hadisin
The Hadīth shows the great status of the prayers and that they are the distinguishing feature between the believer and the disbeliever.
The rulings of Islam are established based on the outward circumstances of people, regardless of their inward circumstances.