The Essence
Al-Muqaddim is the One who brings things forward. He advances whomever He wills in rank, honors some over others, and brings certain events forward in time according to His perfect wisdom.
In the Quran
بَلْ لِلَّهِ الْأَمْرُ جَمِيعًا
"But to Allah belongs the command entirely. (Surah Ar-Ra'd 13:31) - Refers to His command in advancing and delaying."
In Your Duas
أَنْتَ الْمُقَدِّمُ وَأَنْتَ الْمُؤَخِّرُ لاَ إِلَهَ إِلاَّ أَنْتَ
"You are the One who brings forward (Al-Muqaddim) and You are the One who delays. There is no deity except You."
— Sahih al-Bukhari 1120