Is it considered disbelief if a person, during a quarrel, says to their father, "whether God wills or not" (in reference to the father saying "God willing" regarding helping his son with his education), knowing that the words were uttered without thought or intention of disbelief?

This phrase is a grave error that contradicts the universality of Allah's will, and that what Allah wills comes to be, and what He does not will does not come to be, and that nothing occurs in His dominion that He does not desire. Disbelief (kufr) is incurred by this word if its utterer believes that a creature can bring about something Allah did not will, and the lack of intent for disbelief does not benefit. So, whoever says or does what constitutes disbelief, disbelieves thereby, even if they did not intend to be a disbeliever.