So David went, he and the six hundred men that were with him, and came to the brook Besor, where those that were left behind stayed. But David pursued, he and four hundred men: for two hundred abode behind, which were so faint that they could not go over the brook Besor… Then answered all the wicked men and men of Belial, of those that went with David, and said, Because they went not with us, we will not give them ought of the spoil that we have recovered, save to every man his wife and his children, that they may lead them away, and depart. Then said David, Ye shall not do so, my brethren, with that which the LORD hath given us, who hath preserved us, and delivered the company that came against us into our hand. For who will hearken unto you in this matter? but as his part is that goeth down to the battle, so shall his part be that tarrieth by the stuff: they shall part alike. – 1 Samuel 30:9-10; 21-23

If by sickness you are detained at home, if for any other reason, such as age or infirmity, you are not able to enter into actual service, yet if you are a true soldier and would fight if you could, and your heart is in it, you shall share even with the best and bravest of those who, clad in the panoply of God, encounter and grapple with the adversary…(for) the law of the Son of David is the same as the law of David himself; and you know the law of David about those that went to the battle. There were some that were lame, and some that were otherwise incapable of action, and he left them with the baggage. “There,” he said, “you are very weary and ill: stop in the camp: take care of the tents, and the ammunition, while we go and fight.” Now, it happened once on a time that the men that went to fight claimed all the spoil. They said, “These people have done nothing: they have been lying in the trenches: they shall not carry off a share of the booty.” But King David there and then made a law that they should share and share equally-those that were in the trenches and those that engaged in the fray. “As his part is that goeth down to the battle, so shall his part be that tarrieth by the stuff: they shall part alike. And it was so from that day forward, that he made it a statute and an ordinance for Israel.” Nor is the law of the Son of David less gracious. ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/1513.cfm