Following the Newburgh Address Washington famously quelled a potential mutiny by drawing attention to the fact that he was losing his eyesight. It's reported 1 of 2 ways. He either said, "Gentlemen, you will permit me to put on my spectacles, for I have not only grown gray but almost blind in the service of my country" or "Gentlemen, you must pardon me. I have grown gray in your service and now find myself growing blind." The difference and key question is whether he said that he went blind in their (the Officers') service or in service to the country. Small but important point.
Quite honestly we're not sure. The reports on what were said came from various sources who were there, and there were some people present who didn't remember a letter being read at all, and others who do.
Both interpretations are possible. Before Washington read the letter he gave an impassioned speech to the officers who were gathered in which he argued both for the country and for the men.
For example there's this part of his speech which would support the notion that the words were "service to my country":
"This dreadful alternative of either deserting our country in the extremest hour of her distress, or turning our arms against it, which is the apparent object, unless Congress can be compelled into instant compliance, has something so shocking in it, that humanity revolts at the idea. My God! what can this writer^1 have in view, by recommending such measures?. Can he be a friend to the army? Can he be a friend to this country? Rather is he not an insidious foe?"
However he also spends a some time talking about the men and officers he served with:
"For myself, and I take no merit in giving the assurance, being induced to it from principles of gratitude, veracity and justice, a grateful sense of the confidence you have ever placed in me, a recollection of the cheerful assistance and prompt obedience I have experienced from you, under every vicissitude of fortune, and the sincere affection I feel for an army I have so long had the honor to command, will oblige me to declare, in this public and solemn manner, that in the attainment of compleat justice for all your toils and dangers, and in the gratification of every wish, so far as may be done consistently with the great duty I owe my country, and those powers we are bound to respect, you may freely command my services to the utmost extent of my abilities.
While I give you these assurances, and pledge myself in the most unequivocal manner, to exert whatever ability I am possessed of in your favour, let me entreat you, gentlemen, on your part, not to take any measures, which, viewed in the calm light of reason, will lessen the dignity, and sully the glory you have hitherto maintained."
The result of the speech is well known of course. Any thought of rebellion was instantly gone and the men there voted unanimously to support Congress. Thomas Jefferson would later say that "The moderation and virtue of a single character has probably prevented this revolution from being closed as most others have been by a subversion of that liberty it was intended to establish."^2
1.) The writer he's referring to is the author of an anonymous pamphlet that was distributed among the officers and men at Newburgh listing the causes of their dissatisfaction and the solution they wanted.
2.) Letter from Jefferson to Washington written in 1784.
2.) The text of the anonymous pamphlet and of Washington's speech can be found here