What should someone do who made a vow to perform an 'aqiqah if Allah blesses him with a child, but he does not possess the means to buy the sacrificial animal?

It has been established that the Prophet, peace and blessings be upon him, forbade making vows, and he specifically directed this prohibition towards those who believe their purpose will be achieved because of it, as a vow is used to extract from the miser. And whoever vows an act of obedience and then becomes unable to fulfill it, must offer an expiation for a broken oath. So, whoever vows to perform the 'aqiqah for his child, it becomes obligatory upon him. If he is unable to fulfill his vow and had specified a time, he must offer an expiation for a broken oath after the time has elapsed. If he did not specify a time, the 'aqiqah remains a debt upon him until he is able to fulfill it.