The fact that salvation is by the grace of God and not by man’s works is a conclusion justly and explicitly drawn from Scripture. The question, therefore, is: Does salvation by faith contradict salvation by grace? Does salvation by faith imply, in some subtle way, salvation by works. Scripture itself provides a clear answer: “By faith” is not “by works” but is “by grace.”
May I pose a couple of questions for you from the OT, to help you clarify your understanding of grace, faith, and works.
Think back to, or go and reread, the stories of the widow who gave her last cake of bread to the prophet, and of the widow who poured oil from her jar to save the son who was going to be sold to pay her late husband's debts, and of the destruction of the walls of Jericho (there are many more stories like this, but these will get us started).
In each of these stories, was the result (eating from the same bit of flour and oil for the rest of the famine, selling the additional oil to pay the debts, the fall of the walls of Jericho) caused by the grace of God? or by the works of man (or woman)?
In each of these stories, was there a conditional action that the person/people involved were required to perform for the grace of God to bring about the result?
In each of these stories, did the action performed by the person/people involved "earn", "merit", or "deserve" the resulting grace?
There you have the basis for understanding faith, grace, and works.
When God promises something (salvation, sustenance, redemption of debt, conquering the Land, etc.), He almost always places a condition upon the receipt of that gift (grace). If the condition is met, then the grace is received. If the condition is not met, then the grace is not received.