Ramadan daily dua and its benefit.
Rabbana atmim lana noorana waghfir lana;
Innaka ala kulli shay-in qadeer.
Translation
Our Lord, perfect for us our light and forgive us. Indeed, You are over all things competent.
Benefit
Mujahid states that the Believers will recite this Dua at the time when they will see that the celestial light of the Hypocrites had disappeared on the day of Qiyamah.
Ibn Kathir Vol. 4 P. 418/9
On the bridge of Sirat the Believers will see (Nur) celestial light in front of them as well as on their right hand side. When they will see that the (Nur) celestial light of the Hypocrites has disappeared they will recite this Dua.
The (Nur) celestial light will be in proportion to a person's actions. Therefore the Dua is being made to perfect the celestial light.
Mazhari Vol. 11 P. 594
Reference
Surah At-Tahrim 8