Is it permissible to retract a vow to donate a large sum of money (400,0 EGP), made for the healing of one's mother from a stroke, before the healing has occurred, due to remembering other urgent financial obligations?

A conditional vow must be fulfilled if the condition is met, and one cannot be released from it except in cases of inability to do so. As for vowing to donate all one's wealth, there is a difference of opinion among scholars. The view of the Malikis and Hanbalis, which was also chosen by Ibn Taymiyyah and Ibn al-Qayyim, is that one-third of the wealth is sufficient. They based their argument on the hadith of Ka'b ibn Malik, may Allah be pleased with him, when he intended to donate all his wealth, the Prophet, peace and blessings be upon him, said to him: "Keep some of your wealth, for that is better for you." Therefore, whoever vows to donate all his wealth should keep what he and his family need and donate the rest.