Peace be upon you. Is it permissible to open a house of mourning for a deceased child?

Offering condolences is Islamically recommended, regardless of whether the deceased is an adult or a child. This is based on the Prophet's (PBUH) saying: "There is no Muslim who consoles his brother during a calamity except that Allah Almighty will clothe him with garments of honor on the Day of Resurrection." Scholars have differed on the issue of sitting at home to receive condolences; the Malikis permitted it, while others disliked it or considered it contrary to what is preferable. As for opening a condolence house and the accompanying practices that necessitate spending large sums of money, this is not part of the Sunnah (definition).