Bukhari

Hadith Commentary:
In Isma'il's narration, it is mentioned that when we returned to Yemen with Ali (radi Allahu anhu), a group of disbelievers from Hamdan confronted us.
Ali (radi Allahu anhu) recited to them the letter of the Messenger of Allah (sallallahu alayhi wa sallam).
All of them embraced Islam.
Ali (radi Allahu anhu) wrote about this situation to the Messenger of Allah (sallallahu alayhi wa sallam).
He (sallallahu alayhi wa sallam) performed a prostration of gratitude (sujud al-shukr) and said, "May Hamdan remain safe."

Hadith Commentary:
In one narration, it is mentioned that when we returned and went to Yemen with Ali (radi Allahu anhu), we encountered the tribe of Hamdan. Ali (radi Allahu anhu) recited to them the letter of the Messenger of Allah (sallallahu alayhi wa sallam), and all of them embraced Islam. When Ali (radi Allahu anhu) informed the Messenger of Allah (sallallahu alayhi wa sallam) of this incident, he performed a prostration of gratitude (sajdat al-shukr) and said: "May Hamdan remain safe." (Al-Sunan al-Kubra lil-Bayhaqi: 2/369 and Fath al-Bari: 8/83)

In another narration, when the Messenger of Allah (sallallahu alayhi wa sallam) intended to send Ali (radi Allahu anhu) to Yemen, he said: O Messenger of Allah (sallallahu alayhi wa sallam)! You are sending me to a people whose individuals are elderly, while I am still young and do not possess full ability to judge. The Messenger of Allah (sallallahu alayhi wa sallam) placed his hand upon my chest and supplicated: "O Allah! Keep his tongue firm and guide his heart." He also said: "When a matter comes to you, listen to the statements of both parties and then pass judgment." (Musnad Ahmad: 1/111)

Takhrij:
«أخرجه البيهقي: 2 /369، وأخرج البخاري صدر الحديث، المغازي، حديث:4349.»©Explanation:
➊ The Prophet sallallahu alayhi wa sallam performed a prostration of gratitude (sujud al-shukr) upon reading in the letter of Ali radi Allahu anhu the news of the people of Yemen accepting Islam.
The increase in the number of Muslims is a cause for happiness and a source of joy, and this too is a great blessing from Allah; therefore, performing a prostration of gratitude as a form of thanks is legislated.
➋ There was a time when the large number of Muslims used to be a source of happiness and delight, and now this is an era in which schemes and practical measures to prevent the birth of Muslim children are being implemented day and night. And the irony is that this campaign is being run vigorously at the governmental level, and millions are being spent to make it successful.