What to compete over
The width of what is being offered is given as a measurement.
سَابِقُوٓا۟ إِلَىٰ مَغْفِرَةٍ مِّن رَّبِّكُمْ وَجَنَّةٍ عَرْضُهَا كَعَرْضِ ٱلسَّمَآءِ وَٱلْأَرْضِ أُعِدَّتْ لِلَّذِينَ ءَامَنُوا۟ بِٱللَّهِ وَرُسُلِهِۦ ۚ ذَٰلِكَ فَضْلُ ٱللَّهِ يُؤْتِيهِ مَن يَشَآءُ ۚ وَٱللَّهُ ذُو ٱلْفَضْلِ ٱلْعَظِيمِ
Sābiqū ilā maghfiratin min rabbikum wa jannatin ʿarḍuhā ka-ʿarḍi-s-samā'i wa-l-arḍ…
“Race [i.e., compete] toward forgiveness from your Lord and a Garden whose width is like the width of the heavens and earth, prepared for those who believed in Allāh and His messengers. That is the bounty of Allāh which He gives to whom He wills, and Allāh is the possessor of great bounty.”
Source
The Qur'an · 57:21
Qur'an
- Qur'anic text in the Uthmani script via Quran.com; translation: Saheeh International