Wa `alaykum as-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
As for your vow to leave your job, if you just intended it, you do not have to fulfill it. But if you have made it verbally, you can either fulfill or offer the expiation for it.
Responding to your question, Dr. Muhammad Salama, PhD in Islamic Studies in English and an Associate Professor at the Faculty of Islamic Science, Al-Madinah International University, states:
If you have not spoken out your vow, you are not responsible for such intention. But if you have spoken it out, then it is up to you to decide, based on what is better for you, either to fulfill your vow or to break it and give the atonement mentioned in the Qur’an,
“God will not hold you accountable for unintended vows in your oaths. But He will hold you accountable for what you have [intentionally] bound yourselves to by oaths, the atonement of which is feeding ten indigent people with the average of what you feed your own families; or clothing them; or freeing a human being from bondage. But if one [of you] does not find [such means], then fast three days [instead].” (Al-Ma’idah 5:89)
Allah Almighty knows best.