Tafsir of Al-Qamar 54:54

{ وَنَهَرٍ } And [in] a river. It is the plural of nahr (river), like asad (lion) and usud (lions). It uses the generic noun to suffice for the plural. It has also been said: it refers to vastness and the light of the day (nahār). It is also recited with a quiescent hā’ (nahr).

{ فِي مَقْعَدِ صِدْقٍ } In a place of truth; meaning, a place that is pleasing. It is also recited as { fī maqā‘idi ṣidqin } (in places of truth).

{ عِنْدَ مَلِيكٍ مُقْتَدِرٍ } Near a Sovereign, All-Powerful. They are brought near to a Sovereign whose authority and power are absolute and beyond description. There is nothing that is not under His dominion and power. What status could be more honorable than that status, or more encompassing of all joy and complete happiness?

From the Messenger of God, may God bless him and grant him peace: "Whoever recites Surah al-Qamar every other day, God will resurrect him on the Day of Resurrection with his face like the moon on the night of the full moon."