I visited Abu Musa, as he was in the house of the daughter of Fadl b. 'Abbas. I sneezed but he did not respond to it (by saying): Allah may have mercy upon you. Then she sneezed and he (Fadl b. 'Abbas) said: May Allah have mercy upon you. I came back to my mother and informed her about it, and when he came to her she said: My son sneezed in your presence and you did not say:" Allah may have mercy upon you, and she sneezed and you said for her:" May Allah have mercy upon you." Thereupon he said: Your son sneezed but he did not praise Allah and I did not beg mercy of Allah for him and she sneezed and she praised Allah and so I said: May Allah have mercy upon you, as I heard Messenger of Allah ﷺ as saying: When any one of you sneezes he should praise Allah and the other should say: May Allah have mercy upon you, and if he does not praise Allah, no mercy should be begged for him.  

عَطَسَ عِنْدَكَ ابْنِي فَلَمْ تُشَمِّتْهُ وَعَطَسَتْ فَشَمَّتَّهَا فَقَالَ إِنَّ ابْنَكِ عَطَسَ فَلَمْ يَحْمَدِ اللَّهَ فَلَمْ أُشَمِّتْهُ وَعَطَسَتْ فَحَمِدَتِ اللَّهَ فَشَمَّتُّهَا سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ إِذَا عَطَسَ أَحَدُكُمْ فَحَمِدَ اللَّهَ فَشَمِّتُوهُ فَإِنْ لَمْ يَحْمَدِ اللَّهَ فَلاَ تُشَمِّتُوهُ  

[Machine] "I saw Abu Musa in the house of Umm Al-Fadl and she sneezed, so I said 'bless you' but she did not say it to me. When I came to my mother, I told her about it. When Abu Musa came to her, she said to him, 'Your son sneezed and you did not say praise be to Allah, so I did not say it to him. And a woman sneezed and I said it to her.' He replied, 'If your son sneezes and does not praise Allah, do not say it to him.' I heard the Messenger of Allah ﷺ saying, 'When one of you sneezes and praises Allah, say 'bless you' to them. But if they do not praise Allah, do not say it to them.' She said, 'You did well, you did well.'"  

شَهِدْتُ أَبَا مُوسَى وَهُوَ فِي بَيْتِ أُمِّ الْفَضْلِ فَعَطَسَتْ فَشَمَّتُّهَا وَعَطَسْتُ فَلَمْ يُشَمِّتْنِي فَلَمَّا جِئْتُ إِلَى أُمِّي أَخْبَرْتُهَا فَلَمَّا جَاءَهَا أَبُو مُوسَى قَالَتْ لَهُ عَطَسَ عِنْدَكَ ابْنِي فَلَمْ تُشَمِّتْهُ وَعَطَسَتِ امْرَأَةٌ فَشَمَّتُّهَا فَقَالَ إِنَّ ابْنَكِ عَطَسَ فَلَمْ يَحْمَدِ اللَّهَ فَلَمْ أُشَمِّتْهُ وَإِنَّهَا عَطَسَتْ فَحَمِدَتِ اللَّهَ فَشَمَّتُّهَا سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ «إِذَا عَطَسَ أَحَدُكُمْ فَحَمِدَ اللَّهَ فَشَمِّتُوهُ وَإِذَا لَمْ يَحْمَدِ اللَّهَ فَلَا تُشَمِّتُوهُ» قَالَتْ أَحْسَنْتَ أَحْسَنْتَ