To what extent is the hadith authentic which mentions the punishment for not fulfilling a relative's request, by the appearance of "a snake called Al-Aqra'" in the grave?

A Muslim should be generous and giving, especially towards relatives and in-laws, for stinginess is reprehensible. The Quran mentions that one of the characteristics of disbelievers is withholding good, and it criticizes those who show off by withholding even small acts of kindness (al-ma'un). Giving is of two types: obligatory, such as zakat, and recommended, such as voluntary charity and maintaining kinship ties. If a relative requests something that is obligatory for the person being asked (like a trust or a debt), then it is obligatory to give it. As for anything else (like wealth or assistance), it is recommended to give it but not obligatory. And what is not obligatory to do does not entail punishment in the grave or the hereafter. There is no basis for what the questioner mentioned.