Narrated 'Uqba bin 'Amir:

The Prophet went out and offered the funeral prayer for the martyrs of the (battle of) Uhud and then ascended the pulpit and said, "I am your predecessor and I am a witness against you. By Allah, I am now looking at my Tank-lake (Al-Kauthar) and I have been given the keys of the treasures of the earth (or the keys of the earth). By Allah! I am not afraid that after me you will worship others besides Allah, but I am afraid that you will start competing for (the pleasures of) this world."

حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا اللَّيْثُ، عَنْ يَزِيدَ بْنِ أَبِي حَبِيبٍ، عَنْ أَبِي الْخَيْرِ، عَنْ عُقْبَةَ بْنِ عَامِرٍ، أَنَّ رَسُولَ اللَّهِ ﷺ خَرَجَ يَوْمًا فَصَلَّى عَلَى أَهْلِ أُحُدٍ صَلاَتَهُ عَلَى الْمَيِّتِ، ثُمَّ انْصَرَفَ إِلَى الْمِنْبَرِ فَقَالَ
" إِنِّي فَرَطُكُمْ وَأَنَا شَهِيدٌ عَلَيْكُمْ، وَإِنِّي وَاللَّهِ لأَنْظُرُ إِلَى حَوْضِي الآنَ، وَإِنِّي قَدْ أُعْطِيتُ مَفَاتِيحَ خَزَائِنِ الأَرْضِ ـ أَوْ مَفَاتِيحَ الأَرْضِ ـ وَإِنِّي وَاللَّهِ مَا أَخَافُ عَلَيْكُمْ أَنْ تُشْرِكُوا بَعْدِي، وَلَكِنِّي أَخَافُ عَلَيْكُمْ أَنْ تَنَافَسُوا فِيهَا ".