The one condition attached to entering
ʿUthmān narrated it, and it is as short as it sounds.
مَنْ مَاتَ وَهُوَ يَعْلَمُ أَنَّهُ لاَ إِلَهَ إِلاَّ اللَّهُ دَخَلَ الْجَنَّةَ
Whoever dies knowing that there is no god but Allah will enter Paradise.
The full narration
It is narrated on the authority of 'Uthman that the Messenger of Allah (ﷺ) said. He who died knowing (fully well) that there is no god but Allah entered Paradise
Source
Ṣaḥīḥ Muslim · 136
Ṣaḥīḥ
- Agreed upon as authentic (al-Bukhārī / Muslim)