جَنَّـٰتِ عَدْنٍ ٱلَّتِى وَعَدَ ٱلرَّحْمَـٰنُ عِبَادَهُۥ بِٱلْغَيْبِ ۚ إِنَّهُۥ كَانَ وَعْدُهُۥ مَأْتِيًّا
Jannaati 'adninil latee wa'adar Rahmaanu ibaadahoo bilghaib; innahoo kaana wa'duhoo maatiyyaa
they will enter the Gardens of Lasting Bliss, promised by the Lord of Mercy to His servants- it is not yet seen but truly His promise will be fulfilled.
Gardens of Eden, which the Most Merciful has promised to his servants in the unseen. That promise will surely come to pass.
Readers have taken bi'l-ghayb two ways: promised while it remains unseen, or promised to servants who believe in the unseen. The garden is described here as what those who repented in the verse before are given, which keeps the passage on the ones who came back. Al-Rahman is the name that runs through this surah, and it is the name carrying the promise here.