وَاذْكُرْ رَبَّكَ فِي نَفْسِكَ تَضَرُّعًا وَخِيفَةً
Remember your Lord within yourself, humbly and fearfully.
Imam al-Razi relates the following amazing insight in his tafsir:
He, the Most High, said, “Remember your Lord [rabb] within yourself,” and He did not say, “Remember your god [ilaah],” nor any of the other Names. He only named Himself in this position with the name of His being the Lord, and He connected Himself to that. All of that indicates towards the furthest extent of mercy [rahmah], closeness [taqreeb], graciousness [fadl] and benificence [ihsaan]. His intent is to cause the slave to become exultant and happy at hearing this Name; because the word ‘Lord’ imparts a sense of nurturing [tarbiyah] and graciousness. At hearing this Name, the slave recalls the various types of favours [ni’am] of Allah upon him; and in reality, his intellect cannot even reach the least of them. As He, the Most High, has said, “And if you were to count the favours of Allah, you would not be able to enumerate them.” (Ibrahim: 34)
So at the manifestation [inkishaaf] of this rank within the heart, hope becomes strengthened. Then when he hears after that His saying, “…humbly and fearfully,” fear becomes great. Then there is existent within the heart both the causes for hope and the causes for fear. At that, faith [imaan] becomes perfected, according to what he said, peace be upon him, “If the fear of a believer and his hope were to be weighed, they would be balanced.” Except that there is one subtlety – and it is that the hearing of the word ‘Lord’ causes hope, and the hearing of the words ‘humility and fearfulness’ cause fear. So when the beginning occurs with that which causes hope, we come to know that the aspect of hope is stronger.
(Mafateeh al-Ghaib by Imam Fakhruddin al-Razi)