Allah commands His servants to supplicate to Him, for this will ensure their welfare in this life and the Hereafter. Allah said,

﴿ادْعُواْ رَبَّكُمْ تَضَرُّعًا وَخُفْيَةً﴾

(Invoke your Lord Tadarru`an and Khufyah) meaning, in humbleness and humility. Allah said in a similar Ayah,

﴿وَاذْكُر رَّبَّكَ فِي نَفْسِكَ﴾

(And remember your Lord within yourself) ﴿7:205﴾ It is recorded in the Two Sahihs that Abu Musa Al-Ash`ari said, "The people raised their voices with supplications but the Messenger of Allah said,

«أَيُّهَا النَّاسُ ارْبَعُوا عَلَى أَنْفُسِكُمْ فَإِنَّكُمْ لَا تَدْعُونَ أَصَمَّ وَلَا غَائِبًا إِنَّ الَّذِي تَدْعُونَ سَمِيعٌ قَرِيب»

(O people! Take it easy on yourselves. Verily, you are not calling one who is deaf or absent, rather, the One you are calling is All-Hearer, Near (to His servants by His knowledge).) Ibn Jarir said that,

﴿تَضَرُّعًا﴾

(Tadarru`an), means obeying Him in humility and humbleness,

﴿وَخُفْيَةً﴾

(and Khufyah), with the humbleness in your hearts and certainty of His Oneness and Lordship not supplicating loudly to show off.