Prophet Muhammad (PBUH) said: “Be upright, although you will never be able to be virtuous [all the time]. But know that the best of your deeds is prayer and that only the true believer will guard his ablution (wudoo).” Authenticated in Saheeh Sunan Ibn Maajah, vol. 1, p. 151, no. 224. Wudoo is guarded by performing it properly and with the awareness that one is doing it as an act of purification and worship that will bring one closer to Allaah. It is also guarded by renewing one’s state of purity whenever it is broken. The Prophet (PBUH) also recommended making ablution before going to sleep (Sahih Al-Bukhari, vol.1, p.155, no.247) as well as after sexual intercourse (Sahih Al-Bukhari, vol.1, p.174, nos.286 & 288).