The Late Sheikh Jad Al-Haqq `Ali Jad Al-Haqq, former grand Sheikh of Al-Azhar, states: Every Muslim has to fulfill the vow you have made to Allah, i.e., to spend some money in the cause of Allah. Allah Almighty says, “Then let them make an end of their unkemptness and pay their vows and go around the ancient House.” (Al-Hajj: 29)
Also, the Messenger of Allah (peace and blessings be upon him) said, “When you make a vow to do an act of obedience to Allah, you must fulfill it. But if you vowed to disobey Allah, you must never do it.” And, he (peace and blessings be upon him) said, “Every action is based on the intention behind it…”
So, when someone makes a vow with a firm determination to give charity only for the sake of Allah, he can fulfil this by observing good deeds in general, such as establishing mosques and keeping good relations with his family. If his family is in need of financial support, he can dedicate part of his charity to his family, and spend the rest in different charitable channels that are worthy of his aid. By doing so, he will attain the pleasure of Allah and abide by His commands. Allah says, “And whatsoever ye spend (for good) He replaceth it. And He is the Best of Providers.” (Saba’: 39)