Have I erred in refusing a bank job, preferring to travel to work in Saudi Arabia, even though I am still concerned about the ruling on working in banks, and afraid of losing a great financial opportunity, and my father is displeased with my decision?

Working in usurious banks is impermissible because it constitutes aiding in what is forbidden, and usury is one of the gravest major sins that incurs a curse, due to the saying of the Messenger of Allah, peace and blessings be upon him: "The Messenger of Allah, peace and blessings be upon him, cursed the one who consumes usury, the one who feeds it, its scribe, and its two witnesses. He said: 'They are all equal.'" However, working in them is permissible out of necessity for someone who cannot find another permissible job. You have done well by choosing permissible work, even if it is in distant lands, so rejoice in good tidings, for Allah Almighty says: "Indeed, he who fears Allah and is patient, then verily, Allah does not allow to be lost the reward of those who do good." [Surah (definition) Yusuf: 90]