الكافي 3/4/32/4

4. Al-Husayn ibn Muhammad has narrated from Mu‘alla’ ibn Muhammad from al-Washsha’ from Aban ibn ‘Uthman from al-Hassan ibn al-Mughirah who has said the following: “I heard abu ‘Abd Allah عليه السلام , say, ‘The excellence of prayer, after an obligatory Salah (prayer), over prayers after non-obligatory Salah (prayer), is like the excellence of obligatory Salah (prayer) over non-obligatory Salah (prayer).’ The Imam then said, ‘Pray to Allah and do not say that matters are settled. Prayer is worshipping. Allah, the Most Majestic, the Most Glorious, has said, “Those who belittle worshipping Me will go to hell in humiliation.” He has also said, “Pray to Me. I answer your prayers.” (40:60) The Imam then said, ‘When you want to pray to Allah, you should speak of His glory. You should praise Him, speak of His Majesty, say that He is the only Lord who must be worshipped and speak of His praise. You should say, “Allahumma Salli ‘Ala Muhammad wa ‘Ali Muhammad (O Allah grant Muhammad and his family a compensation worthy of their serving Your cause),” then ask for your needs, you will receive what you need.’”