The Prophet said: "Instruct your dying to say: (La illaha illallah) 'None has the right to be worshipped but Allah'  

عَنِ النَّبِيِّ ﷺ قَالَ لَقِّنُوا مَوْتَاكُمْ لاَ إِلَهَ إِلاَّ اللَّهُ قَالَ وَفِي الْبَابِ عَنْ أَبِي هُرَيْرَةَ وَأُمِّ سَلَمَةَ وَعَائِشَةَ وَجَابِرٍ وَسُعْدَى الْمُرِّيَّةِ وَهِيَ امْرَأَةُ طَلْحَةَ بْنِ عُبَيْدِ اللَّهِ  

"The Messenger of Allah said to us: 'When you attend to the sick or dying then say only good, for indeed the angels say "Amin" to what you say.'" She said: "When Abu Salamah died I went to the Prophet and said: 'O Messenger of Allah! Abu Salamah has died.' He said: 'Then say: "O Allah forgive me and him, and give me a good replacement for him." She said: "I said tat, and Allah gave a replace that was better than him: The Messenger of Allah."  

لَنَا رَسُولُ اللَّهِ ﷺ إِذَا حَضَرْتُمُ الْمَرِيضَ أَوِ الْمَيِّتَ فَقُولُوا خَيْرًا فَإِنَّ الْمَلاَئِكَةَ يُؤَمِّنُونَ عَلَى مَا تَقُولُونَ قَالَتْ فَلَمَّا مَاتَ أَبُو سَلَمَةَ أَتَيْتُ النَّبِيَّ ﷺ فَقُلْتُ يَا رَسُولَ اللَّهِ إِنَّ أَبَا سَلَمَةَ مَاتَ قَالَ فَقُولِي اللَّهُمَّ اغْفِرْ لِي وَلَهُ وَأَعْقِبْنِي مِنْهُ عُقْبَى حَسَنَةً قَالَتْ فَقُلْتُ فَأَعْقَبَنِي اللَّهُ مِنْهُ مَنْ هُوَ خَيْرٌ مِنْهُ رَسُولَ اللَّهِ ﷺ