What is the ruling on one who swore when he was thirteen or fourteen years old that he would be an infidel if he committed a certain sin, then committed this sin believing that his oath would not be held against him due to his young age, and continued to commit the sin until he was twenty-three years old, at which point he regretted it and became aware? Is he considered an infidel and outside the fold of Islam, or is his oath void?

If someone swears that they are an unbeliever (kafir) if they do such-and-such, and then they do it, they have committed a grave sin. However, they do not become an unbeliever by this, unless they harbored disbelief in their heart. No expiation (kaffarah) is incumbent upon them, whether they are legally competent (mukallaf) or not. If they harbored disbelief in their heart and were legally competent, then they become an unbeliever. As for a minor (ghair mukallaf), there is a difference of opinion among jurists regarding the ruling on a minor's apostasy. And whoever regrets their action and did not harbor disbelief should repent to Allah with sincere repentance and refrain from this objectionable oath.