سورة Al-Baqarah ( The Cow ) - الآية 45

And seek help in patience and As-Salat (the prayer) and truly it is extremely heavy and hard except for Al-Khashi'un [i.e. the true believers in Allah - those who obey Allah with full submission, fear much from His Punishment, and believe in His Promise (Paradise, etc.) and in His Warnings (Hell, etc.)].