The saint’s watchword. What is that?

“This is the heritage of the servants of the Lord, and their righteousness is of Me, saith the Lord.” – Isaiah 54:17

In ancient times, if not at present, armies used to have their watchwords, by which they might recognize one another in the dark. We want a watchword now. It is very difficult to tell the children of God unless we have certain signs. God Himself gives us the watchword. “Your righteousness is of Me, saith the Lord.” You can always tell a saint of God by this watchword. If he says, “My righteousness is of God,” you may safely believe that he is a disciple of Jesus Christ. If he does not understand our shibboleth, he may not have lived in that country where they speak the pure language of Canaan, and that may excuse defects in his language. He may differ from us in some points, but if he sincerely says, “My righteousness is of God,” you may safely conclude that he is not an enemy of truth. I mean “THE TRUTH as it is in Jesus.”

O, there is to be a time when God’s children shall come out clear of all slander, when falsehood shall be swept away, and they shall stand forth justified even by their enemies. Their slanderers shall have nothing to say against them. They shall share in the admiration which an assembled universe shall be constrained to give to Him who doeth all things well. But this vindication will not be brought about by their own efforts. They have not been anxious to avoid reproach for Christ’s sake. They have not wept and bemoaned themselves because they were counted the offscouring of all things. No; their righteousness, their entire clearing from the aspersions of malice and the calumnies of envy will come from Jehovah…The character of the saints God Himself shall vindicate, and all liars shall have their portion in the lake of fire and brimstone. ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/2908.cfm