Note 2 at Lu 1:6: Zacharias and Elizabeth were not righteous (or literally, in right standing with God) through their own goodness (Isa 64:6 and Ro 3:10), but their faith was accounted to them as righteousness, just as with Noah (Heb 11:7) and Abraham (Ro 4:3). Even under the Old Testament, the only way to be in right standing with God was by faith (Hab 2:4 and Ga 3:11). No one could keep the Law perfectly (Ro 3:23), so faith had to be put in the mercy and forgiveness of God, which was illustrated by the Old Testament blood sacrifices. The Jewish nation as a whole lacked the understanding of justification by faith (Ro 10:3-9) and had fallen into the deception that they could be righteous by their keeping the Law (Mr 10:17). Notice here in this verse that the scripture doesn't say that Zacharias and Elizabeth were sinless but rather blameless. Through their faith in the blood sacrifices (which were symbolic of Christ), God put the blame for their sins on the Lamb (Joh 1:29).