John Calvin Commentary Zechariah 7:10

"and oppress not the widow, nor the fatherless, the sojourner, nor the poor; and let none of you devise evil against his brother in your heart." — Zechariah 7:10 (ASV)

He mentions here some other duties, but for the same purpose of showing that the fear of God is not proved by ceremonies, but by acting justly towards our neighbors. It is not proved by merely abstaining from doing wrong, but by being ready to help the miserable. Since widows, orphans, and strangers are, as if, exposed to plunder, Moses often in the Law commends them to favor, showing that God cares for them and will be their defender when they are injured by anyone.

So also the Prophet speaks here explicitly of widows, orphans, and strangers, so that the Jews might understand that they were not only to be careful that no wronged person should complain, or that no one should retaliate an injury, but that they were to maintain integrity before God. For the ungodly are often terrified by fear and refrain from doing harm, because they know that there will be an avenger.

This is why the rich and the opulent are safe from all injuries, because they are surrounded and fortified by strong defenses; but widows and orphans are not similarly able to repel wrongs. This is the reason the Prophet chooses here to mention widows, orphans, and strangers, rather than to speak generally of all the people. For the meaning of the whole passage is, as I have reminded you, that the fear of God is not truly proven, except when a person adheres to what is just and right. This person is not restrained by fear or shame, but fulfills their duty as if in the presence of God and His angels, showing favor to the poor and miserable who have no one to help them. But as I have elsewhere explained this subject in greater detail, it is sufficient now to touch on it briefly. Let us proceed—