Prayer is the essence of worship

(ALL TRANSLATIONS OF QUR'AAN AND HADITH ON PRAYER)

"Truly, to a happy state shall attain the believers: those who humble themselves in their prayer, and who turn away from all that is frivolous, and who are intent on inner purity." [Qur'an 23:1-4]

"And I have chosen you, so listen to that which is inspired to you.
Verily, I am Allah! There is none worthy of worship but I, so worship Me and offer prayer perfectly for My remembrance." [Taha 13-14]

Be ever mindful of prayers, and of praying in the most excellent way;
and stand before God in devout obedience. [Qur'an 2:238]

And before God prostrate themselves, willingly or unwillingly, all things and beings that are in the heavens and the earth, as do their shadows in the mornings and the evenings. [Qur'an 13:15]

O you who believe! Seek help in patience and prayer. Truly! Allah is with the patient." [surah al Baqarah; 2:153-154]

Verily, the prayer keeps one from the great sins and evil deeds" [al Ankabut 45]

Extol, then, God's limitless glory when you enter upon the evening hours, and when you rise at morn; and seeing that unto Him is due all praise in the heavens and earth, glorify Him in the afternoon as well,
and when you enter upon the hour of noon. [Qur'an 30:17-18]

Our Lord (glorified and exalted be He) descends each night to the earth's sky when there remains the final third of the night, and He says:
"Who is saying a prayer to Me that I may answer it? Who is asking something of Me that I may give it him? Who is asking forgiveness of Me that I may forgive him?" [Hadith Qudsi 35]

The Apostle of Allah was asked: Which of the actions is best? He replied: Observing prayer early in its period. [abu Dawud 2: 426]

The first matter that the slave will be brought to account for on the Day of Judgment is the prayer. If it is sound, then the rest of his deeds will be sound. And if it is bad, then the rest of his deeds will be bad." [at Tabarani]
If a person had a stream outside his door and he bathed in it five times a day, do you think he would have any filth left on him?" The people said, "No filth would remain on him whatsoever." The Prophet (peace be upon him) then said, "That is like the five daily prayers: Allah wipes away the sins by them."
[Sahih al Bukhari, Muslim]
Salat is a pillar of the religion (Islam).
He who establishes it, establishes religion;
and he who destroys it, destroys religion."
[Tabrani]

One of the Saliheen was asked how he kept
his khushu' in prayer (concentration & humbleness etc)
He said, 'I imagine that Allah is before me,
that the Angel of Death is at my back,
that the gardens of Jannah are to my right,
that the fires of Jahannum are on my left
and that I am standing on the Sirat'