Deliberate renunciation is the worst sin.
One day, a woman approached Moses and said, "I am making a terrible mistake." So please pray to Allah that He may forgive me. Then Moses said, "What have you done?" The woman said that I am adultery and later killed the child born as a result. Prophet Moses said, "O sinful woman! Get out of here. Otherwise, fire will come down from heaven and destroy all of us because of your sins.
The woman went away with a broken heart. Then Gabriel came down from the sky and asked, "O Moses! Why did you return this tawari lady? Do not you know about the worst sinner? "
Prophet Moses (peace be upon him) said: Who is more serious than sinful? The Prophet Gabriel said, "The person who abandons his prayer regularly willfully."