1. اَلْحَمْدُ للهِ.
Praise be to Allah.
The Messenger of Allah ﷺ said, “If anyone of you sneezes, he should say [the above].” (Bukhārī 6224)
The Messenger of Allah ﷺ said, “Allah likes sneezing and dislikes yawning, so if someone sneezes and then praises Allah, then it is obligatory on every Muslim who heard him, to say: May Allah have mercy on you (Yarḥamuka-llāh). But as regards yawning, it is from Shaytan, so one must try one’s best to stop it, if one says ‘Ha’ when yawning, Shaytan will laugh at him.” (Bukhārī 6223)
Two men sneezed before the Prophet ﷺ. The Prophet ﷺ said to one of them, “May Allah bestow His Mercy on you,” but he did not say that to the other. On being asked (why), the Prophet ﷺ said, “That one praised Allah (at the time of sneezing), while the other did not praise Allah.” (Bukhārī 6221)
The Messenger of Allah ﷺ said, “The rights of a Muslim on the Muslims are six. It was said to him: “O Messenger of Allah ﷺ, what are these?” He replied: “When you meet him, offer him greetings; when he invites you to a meal accept it, when he seeks your council give him, and when he sneezes and says: “All praise is due to Allah,” you reply; and when he fails ill visit him; and when he dies follow his funeral. (Muslim 2162)
Your companion should reply:
2. يَرْحَمُكَ اللهُ.
May Allah have mercy on you.
The Messenger of Allah ﷺ said, “If anyone of you sneezes, he should say ‘Al-ḥamdu li-llāh’ (Praise be to Allah), and his (Muslim) brother or companion should say to him, [the above]. (Bukhārī 6224)
Then you should say:
3. يَهْدِيْكُمُ اللهُ وَيُصْلِحُ بَالَكُمْ.
May Allah guide you and put your affairs in order.
Yahdīkumu-llāhu wa yuṣliḥu bālakum.
The Messenger of Allah ﷺ said, ” If anyone of you sneezes, he should say ‘Al-ḥamdu li-llāh’ (Praise be to Allah), and his (Muslim) brother or companion should say to him, ‘Yarḥamuka-llāh’ (May Allah bestow his Mercy on you). When the latter says ‘Yarḥamuka-llāh”, the former should say [the above].”(Bukhārī 6224)
The Jews used to try to sneeze in the presence of the Prophet ﷺ hoping that he would say to them: “Allah have mercy on you!” but he would say: [the above].” (Abū Dāwūd 5038)