What should a Muslim do if his infidel parents reject his Islam and threaten to hang him to force him to return to their religion?

A time will come upon the people when the one who holds onto his religion will be like one grasping a burning coal. Beware lest they tempt you away from some of what Allah has revealed to you. You must flee with your religion to where you find someone who will assist you in upholding the truth. And whoever emigrates in the cause of Allah will find on the earth much refuge and abundance. Pray for your family that Allah may guide them and open their hearts to Islam.