Question: Besides Genesis 15:6 concerning Abraham, can you give me other verses that state that the ...

Question: Besides Genesis:15:6And he believed in the LORD; and he counted it to him for righteousness.
See All... concerning Abraham, can you give me other verses that state that the Old Testament saints were declared righteous by their faith in God? 

Response: We are told, “For the law having a shadow of good things to come, and not the very image...can never with those sacrifices which they offered year by year...make the comers thereunto perfect. For then would they not have ceased to be offered? because...the worshippers once purged should have had no more conscience of sin. But in those sacrifices there is a remembrance again made of sins every year. For it is not possible that the blood of bulls and of goats should take away sins” (Heb:10:1-4 [1] For the law having a shadow of good things to come, and not the very image of the things, can never with those sacrifices which they offered year by year continually make the comers thereunto perfect. [2] For then would they not have ceased to be offered? because that the worshippers once purged should have had no more conscience of sins. [3] But in those sacrifices there is a remembrance again made of sins every year. [4] For it is not possible that the blood of bulls and of goats should take away sins.
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Clearly, if the sacrifices demanded by the Law cannot take away sins or provide salvation, then salvation must be by faith in something else. Paul continues, “But that no man is justified by the law in the sight of God...is evident:...The just shall live by faith” (Gal:3:11But that no man is justified by the law in the sight of God, it is evident: for, The just shall live by faith.
See All...). We can’t say that this passage refers only to the New Testament, because Paul is quoting Habakkuk:2:4Behold, his soul which is lifted up is not upright in him: but the just shall live by his faith.
See All..., part of the Old Testament. Consequently, salvation by faith apart from the Law must be an Old Testament principle. Paul stated that the Law was “our schoolmaster [guardian/tutor] to bring us to Christ, that we might be justified by faith” (Gal:3:24Wherefore the law was our schoolmaster to bring us unto Christ, that we might be justified by faith.
See All...). Paul also makes the point that keeping the Law did not save either Old or New Testament Jews because “Therefore by the deeds of the law there shall no flesh be justified in his sight: for by the law is the knowledge of sin” (Rom:3:20Therefore by the deeds of the law there shall no flesh be justified in his sight: for by the law is the knowledge of sin.
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Even the Old Testament sacrificial system prefigured salvation by faith alone. Speaking of the priestly garments, Ezekiel wrote that “they shall have linen bonnets upon their heads...linen breeches upon their loins; they shall not gird themselves with any thing that causeth sweat” (Ezk 44:18).

Man was to “earn” his living by “the sweat of thy face...” (Gen:3:19In the sweat of thy face shalt thou eat bread, till thou return unto the ground; for out of it wast thou taken: for dust thou art, and unto dust shalt thou return.
See All...). But nothing that involves “work” will “earn” you salvation. The Lord’s commands concerning construction of an altar further reinforced this theme: “An altar of earth thou shalt make unto me, and shalt sacrifice thereon thy burnt offerings, and thy peace offerings... in all places where I record my name I will ...bless thee. And if thou wilt make me an altar of stone, thou shalt not build it of hewn stone: for if thou lift up thy tool upon it, thou hast polluted it” (Ex 20:24-25; See also Leviticus:14:32This is the law of him in whom is the plague of leprosy, whose hand is not able to get that which pertaineth to his cleansing.
See All... for similar thoughts).

Paul demonstrates that the Old Testament way of salvation was the same as in New Testament times, pointing to Abraham, who was saved by faith: “Abraham believed God, and it was counted unto him for righteousness” (Rom:4:3For what saith the scripture? Abraham believed God, and it was counted unto him for righteousness.
See All...). For scriptural proof, Paul references Genesis:15:6And he believed in the LORD; and he counted it to him for righteousness.
See All..., pointing to Abraham, who could not have found salvation by keeping the Law, which was still more than 400 years in the future for him. He then singles out David, who was also saved by faith (Rom:4:6-8 [6] Even as David also describeth the blessedness of the man, unto whom God imputeth righteousness without works, [7] Saying, Blessed are they whose iniquities are forgiven, and whose sins are covered. [8] Blessed is the man to whom the Lord will not impute sin.
See All...), quoting Psalm:32:1-2 [1] (A Psalm of David, Maschil.) Blessed is he whose transgression is forgiven, whose sin is covered. [2] Blessed is the man unto whom the LORD imputeth not iniquity, and in whose spirit there is no guile.
See All.... Paul goes further in establishing that in the Old Testament, salvation was by faith only, writing in Romans:4:23-24 [23] Now it was not written for his sake alone, that it was imputed to him; [24] But for us also, to whom it shall be imputed, if we believe on him that raised up Jesus our Lord from the dead;
See All..., “Now it was not written for his sake alone, that it was imputed to him....” Simply put, righteousness is “imputed” (“credited” or “given”) to those with faith in God, e.g., Abraham, David, and now us who are saved by faith.