on pain of
Used to warn of consequences if a specified act is done or not done: subject to the punishment of (some penalty); or (generally) subject to the circumstance of (some thing).
Synonyms: under pain of, upon pain of
We should all be obliged to appear before a board every five years and justify our existence... on pain of liquidation. George Bernard Shaw
And yet we must believe, on pain of being communal, that no system of law has guaranteed as many rights to women as shariah, that no religion is as solicitous of them as Islam. ... The argument can fool no one but the determined apologist. Arun Shourie
Weave the circle, tightly sewn, Let nothing evil or unknown Enter within. Stay without On pain of death, we cast you out. Yasmine Galenorn
All persons are commanded to keep silent, on pain of imprisonment.” Source: Internet
All persons are commanded to keep silent on pain of imprisonment, while the House of Representatives is exhibiting to the Senate of the United States articles of impeachment against Donald John Trump, president of the United States.” Source: Internet
As a result, the Misses Steele are turned out of the house, and Edward is ordered to break off the engagement on pain of disinheritance. Source: Internet