your intention when making this vow was to prevent yourself from hitting your wife rather than intending it to be an act of obedience and drawing closer to Allah, it is obligatory on you to make Kaffarah (expiation) for breaking an oath, according to the correct scholarly view, for it falls under the ruling of oaths. However, if you meant by your vow, along with your intention to prevent yourself from hitting your wife, to draw closer to Allah (Glorified be He), if it happens that you hit her in the future, you have to fulfill the vow you made by slaughtering ten camels all at one time or at different times, according to your ability, and giving the meat to the poor as Sadaqah (voluntary charity). Allah (Glorified be He) says:
So keep your duty to Allâh and fear Him as much as you can
(Part No. 23; Page No. 318) May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.