Is the saying "May God guide you and set your affairs in order" obligatory like "Yarhamukallah" (May God have mercy on you, said to one who sneezes), or is it merely recommended, given the lack of evidence for its obligation?

The Hanbali school of thought holds that responding to someone who sneezes is obligatory, and this is strongly supported by the apparent command of the Prophet, peace and blessings be upon him, who said: "May Allah guide you and rectify your affairs." It is also narrated: "May Allah forgive us and you." Imam An-Nawawi mentioned that this saying is recommended, not obligatory. However, the first opinion (that of the Hanbali school) is more cautious.