PSS

Someone found the lines and I now have them:

Credit to Prof. Prokopovicz, author of Did Lincoln Own Slaves? and Other Frequently Asked Questions about Abraham Lincoln, for finding them:

Act IV, scene ii. King Henry is talking with two soldiers (John Bates and Michael Williams) the night before Agincourt. They don't recognize him in the darkness. Henry points out that the king's cause is just.

WILLIAMS That's more than we know.

BATES Ay, or more than we should seek after; for we know enough, if we know we are the kings subjects: if his cause be wrong, our obedience to the king wipes the crime of it out of us.

WILLIAMS But if the cause be not good, the king himself hath a heavy reckoning to make, when all those legs and arms and heads, chopped off in battle, shall join together at the latter day and cry all 'We died at such a place;' some swearing, some crying for a surgeon, some upon their wives left poor behind them, some upon the debts they owe, some upon their children rawly left. I am afeard there are few die well that die in a battle; for how can they charitably dispose of any thing, when blood is their argument? Now, if these men do not die well, it will be a black matter for the king that led them to it; whom to disobey were against all proportion of subjection.

The reviewer mistakenly attributes this speech to Henry. It does however make sense that Lincoln would be keenly aware of this scene, as the responsibility of command bore heavily on him.