A man may rot even here.

Source

Edgar has returned to Gloucester, an older figure who is later revealed as Edgar's father, and is encouraging him to escape. Gloucester feels he cannot travel further and says his hiding place is fine for him to die.

King Lear, 5. 2  

Act 5, Scene 2

	Original Text	Modern Text
	Alarum within Enter with drum and colors the powers of France over the stage, and CORDELIA with her father LEAR in her hand And exeunt	Sounds of battle offstage. CORDELIA enters hand in hand with LEAR, accompanied by drums, banners, and French troops. They cross the stage and exit.
	Enter EDGAR disguised and GLOUCESTER	EDGAR enters, disguised, along with GLOUCESTER.
	EDGAR Here, father, take the shadow of this tree For your good host. Pray that the right may thrive. If ever I return to you again, I’ll bring you comfort.	EDGAR Here, father, rest awhile in the shade of this tree. Say a little prayer for our side in battle. If I ever come back, I’ll bring you good news.
	GLOUCESTER    Grace go with you, sir.	GLOUCESTER Good luck, sir.
	Exit EDGAR	EDGAR exits.
	Alarum and retreat within	Sounds of battle offstage. They grow fainter.
	Enter EDGAR	EDGAR returns.
5	EDGAR Away, old man. Give me thy hand. Away! King Lear hath lost, he and his daughter ta'en. Give me thy hand. Come on.	EDGAR We have to get out of here, old man. Let me help you up. Let’s go! King Lear’s been defeated. He and his daughter are captured. Give me your hand. Come on.
	GLOUCESTER No further, sir. A man may rot even here.	GLOUCESTER I can’t go any further, sir. This is as good a place as any to die.
10	EDGAR What, in ill thoughts again? Men must endure Their going hence even as their coming hither. Ripeness is all. Come on.	EDGAR Are you depressed again? You can’t choose your time of death any more than your time of birth. We live and die when our time comes. Come on.
	GLOUCESTER    And that’s true too.	GLOUCESTER And that’s true too.
	Exeunt	They exit.

  --William Shakespeare (1564-1616)

Edgar is saying that all men must wait for their time to die and must put up with whatever comes before then. The assumption behind this interpretation is that the time to die is determined by God (very reasonable given Shakespeare's time) and its implied additional meaning is that all men must do what they honorably can to keep themselves alive until their time comes - in this specific instance, by not giving themselves up to the oncoming enemy soldiers.

Men must endure-CLIVE STAPLES LEWIS (1898–1963)