Muslims do it five times a day. - Pray, that is.
Prayer is one of the Five Pillars of Islam, the five duties incumbent on every Muslim. These duties are Shahadah (profession of faith), Salah (ritual prayer), Zakah (alms tax), Sawm (fasting during Ramadan), and Hajj (pilgrimage to Mecca). The five pillars are not explicitly presented as the 'five pillars' in the Qur'an. The concept of the five pillars was presented in the Hadith collections (most notably in the Sahih al-Bukhari and Muslim), based on references to each duty's practice in the Qur'an.
"And perform the prayer." - al-Qur'an 2:43
The Prophet said, "On the night I was taken from Mecca to Jerusalem, Allah imposed fifty obligatory prayers upon my Ummah. So I kept petitioning Him in the matter, asking they be lightened, until He made them but five each day and night." - read al-Bukhari and Muslim.
The five obligatory prayers are: Fajr, Dhuhr, 'Asr, Maghrib and 'Isha', corresponding (relatively) to dawn, noon, afternoon, sunset and night.
