Anas reported: A man among the companions of the Prophet passed away and another man said, “Receive glad tidings of Paradise!” The Messenger of Allah, peace and blessings be upon him, said, “Certainly, you do not know for sure! Perhaps he spoke of what does not concern him, or he was miserly with what would not disadvantage him.”
Source: Sunan al-Tirmidhī 2316
Grade: Sahih li ghayri (authentic due to external evidence) according to Al-Albani
عَنْ أَنَسٍ قَالَ تُوُفِّيَ رَجُلٌ مِنْ أَصْحَابِهِ فَقَالَ يَعْنِي رَجُلًا أَبْشِرْ بِالْجَنَّةِ فَقَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَوَلَا تَدْرِي فَلَعَلَّهُ تَكَلَّمَ فِيمَا لَا يَعْنِيهِ أَوْ بَخِلَ بِمَا لَا يَنْقُصُهُ
2316 سنن الترمذي كتاب الزهد باب فيمن تكلم بكلمة يضحك بها الناس
2882 المحدث الألباني خلاصة حكم المحدث صحيح لغيره في صحيح الترغيب