Is it permissible to swear that whatever befalls a person is good, even if that good has not yet become apparent to him?

Everything that happens to the patient believer is considered good for him. If something good happens to him, he thanks Allah, and that is good for him. And if something bad happens to him, he perseveres, and that is good for him. Allah tests the believer to elevate his status and expiate his sins. If Allah wills good for His servant, He hastens his punishment in this world. And He may test him with what he dislikes to enable him to reach a rank he would not attain through his actions. Based on this, there is no harm in the aforementioned oath.