Here "by faith" refers to placing one's trust in Christ. You can make this explicit in your translation. AT: "because God made them right with him when they trusted in Christ" (See: [[rc://en/ta/man/translate/figs-explicit]])
This means that the Israelites could not please God by trying to keep the law. You can make this explicit in your translation. AT: "were not able to please God by keeping the law because they could not keep it" (See: [[rc://en/ta/man/translate/figs-explicit]])