I have 2 questions In Sha Allah. Firstly, when I fast, is it permissible to lick the lips, as they become quite dry? Also, after I wake up, I always have to spit, because I think that I have licked the pillow or something, but should I have to do this? Secondly if you make an oath, (for example, "I won't say such and such") and forgetfully break it, then I have read that it doesn't require expiation. However, if you forgetfully break the oath, and then think you have broken it and say "such and such" would this require expiation because you didn't break it the first time because of forgetfullness, but you thought it was broken, so you did it? jazakallah , and may Allah reward you.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

If a fasting person licks his lips without moistening them with his saliva, then this is permissible and his fast is not invalidated due to that.

However, if one puts his saliva on his lips and then he licks his saliva from them [his lips], then we have already clarified in previous Fataawa that this invalidates his fasting.

Ash-Sharh Al-Kabeer, one of the books of the Hanbali school of jurisprudance, reads: “If one’s saliva comes out to his clothes or between his fingers or between his lips and then he swallows it again, or that he swallows the saliva of another person, then, in this case, his fast is invalidated because he swallowed it from other than his mouth, it is exactly as if he swallowed something else other than the saliva.” [End of quote].

On the other hand, you are not obliged to spit when you wake up on the pretext that you may have licked something (while sleeping); this is nothing but an instance of severe whispers of Satan, so you should be careful about this and not open a door (to whispers) which would be very difficult for you to close.

As regards the oath, if one breaks it out of forgetfulness, then he is not required to offer expiation for it as per the view we adopt here at Islamweb. However, his oath does not become ineffective by breaking it out of forgetfulness, but it still exists in a way that if he breaks it afterwards knowingly, he is obliged to offer expiation.
Asna Al-Mataalib, one of the books of the Shaafi'i school of jurisprudance, reads: “The oath does not become ineffective if one does what he made an oath on (i.e., not to do) out of forgetfulness or ignorance or compulsion.” [End of quote].

Also, Ar-Ruhaybaani, from the Hanbali school of jurisprudence, said: "One’s oath does not become ineffective if he breaks it in one of these (three) cases.” [End of quote].

However, if one breaks his oath deliberately while believing that his oath no longer exists by what he did out of forgetfulness, then it appears from the statements of the scholars that he broke his oath (i.e. the expiation would be required) unless he was emulating a scholar who issued him a Fatwa to this effect.

Sharh Al-Bahjah, one of the books of the Shaafi'i school of jurisprudance, reads: “If he does something (what he made an oath not to do) while believing that his oath has become ineffective by what he did out of forgetfulness for example, then he is not breaking his oath if he relied on a Fatwa (to this effect) even if it was issued by a person who is not a scholar. However, if he did not rely on any Fatwa but he acted according to his judgment that his oath no longer exists, then he is breaking his oath…...” [End of quote].

Accordingly, if you had done what you made an oath not to do just because of thinking that your oath no longer exists without relying on a Fatwa, then in this case you broke your oath and you are obligated to expiate for it.

 Allaah Knows best.