Taha 20:14

إِنَّنِي أَنَا اللَّهُ لَا إِلَٰهَ إِلَّا أَنَا فَاعْبُدْنِي وَأَقِمِ الصَّلَاةَ لِذِكْرِ‌ي (Surely I am ALLAH. There is no god but I, so worship Me and establish Salah for My remembrance - 20:14): with these words Allah Ta` ala bestowed upon Sayyidna Masu (علیہ السلام) knowledge of all the basic principles of the true Faith, namely the Oneness of Allah Ta` ala, the prophethood and the Hereafter. فَاسْتَمِعْ لِمَا يُوحَىٰ (So listen to what is revealed) refers to prophethood. فَاعْبُدْنِي means "worship Me alone and no one else". This points to the Oneness of Allah Ta` ala.إِنَّ السَّاعَةَ آتِيَةٌ (Surely, the Hour has to come) points to the inevitability of the Hereafter. Although the word فَاعْبُدْنِي (worship Me) encompasses the injunction for prayers also yet it has been mentioned separately to stress its special merit relative to the other forms of worship. It is the pillar of the Faith and its neglect is the mark of the infidels.

أَقِمِ الصَّلَاةَ لِذِكْرِ‌ي (Establish Salah for My remembrance - 20:14): means that the essence of prayer is the remembrance of Allah Ta` ala and that the Salah, from beginning to end is nothing but remembering Allah - with the tongue, the heart and the other organs of the body. Therefore, one should not neglect to remember Allah Ta` ala while praying. This sentence also means that if a person omits to say his prayers at the appointed time due to over-sleeping or forgetfulness while engrossed in some other task, he should say his prayers as soon as he wakes up from sleep or becomes aware of his lapse. This is according to Hadith.