Commentary
The word 'al-wasilah' in: يَبْتَغُونَ إِلَىٰ رَبِّهِمُ الْوَسِيلَةَ
seek the means of close ness to their Lord conveys the sense of that which is used as a means of reaching someone. As for reaching Allah, the wasilah or means is to always keep the pleasure of Allah in sight when learning or doing anything while adhering to the injunctions of the Shari` ah strictly. Thus, the sense of the sentence is that all of them are seeking the closeness of Allah Ta’ ala through their righteous deeds.
About the sentence which follows immediately after: يَرْجُونَ رَحْمَتَهُ وَيَخَافُونَ عَذَابَهُ
hope for His Mercy and fear His punishment, Sahl ibn ` Abdullah said: Hope and Fear, that is, hoping for mercy from Allah as well as fearing Him are two different states one is in. When they stay at par, one keeps on course, correct and stable. And if any one of the two overcomes the other, one finds the equilibrium of his spiritual state subjected to disorder to the measure of that imbalance. (Qurtubi)