It was narrated that 'Abdullah bin 'Amr said:
"The Messenger of Allah said: 'Adhere to righteousness even though you will not be able to do all acts of virtue. Know that among the best of your deeds is prayer and that no one maintains his ablution except a believer.'"
English reference: Vol. 1, Book 1, Hadith 278
Arabic reference: Book 1, Hadith 291