The Muslim must pray 5 times a day. As it is written in Vol. 1 - Salat Book VIII. 345. Narrated Abu Dharr.
50 prayers were reduced to 5 prayers by Mohammeds bargaining with his god. It is because the Muslim can not bear it to pray any more. It is too difficult for him.
The Christian prays without ceasing. The Christian is able to bear it and rejoice in it.
"Rejoice always; pray without ceasing; in everything give thanks; for this is God’s will for you in Christ Jesus." 1 Thessalonians 5:16-18www.gracechurch.org/About/Gospel