stand fast/firm

stand fast

To remain determined, stalwart, and unyielding, as in one's position or opinion. Though it may be hard, we must stand fast in our pledge to environmental reform.
See also: fast, stand

stand firm

To remain determined, stalwart, and unyielding, as in one's position or opinion. Though it may be hard, we must stand firm in our pledge to environmental reform.
See also: firm, stand

stand ˈfast/ˈfirm

refuse to move back; refuse to change your opinions or behaviour: The management have stood firm against demands for a pay increase. OPPOSITE: shift your ground
Fast here means ‘firmly fixed’.
See also: fast, firm, stand