I was about to go to sleep and I was thinking about waking up for Fajr and all of sudden in my head I said “Wallahi I will wake up for Fajr.” I didn’t mean to do it and I didn’t mean the oath.It was on accident. The next night the same thing happened and none of my alarms for Fajr rang so I didn’t wake up. a Do I have to do an expiation? (fast for 3 days)
Alsalam alikum brother/syster. The prophet [pbuh] said
Allah has accepted my invocation to forgive what whispers in the hearts of my followers, unless they put it to action or utter it.source
So inshallah everything that you have in your head or say in your heart is not counted. Other then that the ulmah of our ummah alla agree that for oath to be valid it has to be said verbally and not only in the heart.
Regardless on what ever i said before praying fajer is a fared and me saying what i said before shouldn't stop you from trying, we have to try pur best to try to weak up for fajer.
Hope that answers your question. Allah knows best.