Luke 1:36, “Behold, your relative Elisabeth in her old age has also conceived a son, and this is the sixth month with her who was called barren.”
Luther connects this with Scripture’s pattern to couple promises with signs. When God promises, the ancient saints have often asked for a sign, such as Moses (Exodus 4:1-17), Gideon, (Judges 6:36-40), and, of course, the unbelieving Jews (Matthew 12:38-39). Such demands is putting God to the test, which, Luther says, “Putting God to the test is linked with doubting” (Church Postil, sermon for the Sunday after Christmas on Galatians 4:1-7, LW 75:392-393).
Most unusual here, as was the case with Abraham, Mary the theotokos (mother of God) receives a sign from God without her asking for it. She already believed (Luke 1:34). Here, she said in essence, “I believe you, but how can I conceive when I am a virgin?” Her belief is why she was not cursed as Zechariah was cursed in his unbelief (Luke 1:18-20). Thus, Mary’s question is not from doubt, but faith, and a faith that sought to understand. She already believed and by faith sought to fathom how this would be; she did not need a reason to believe God.
What does this mean for you and me? Remember your Baptism. Baptism is both the sign and the promise that you are a child of God and will, therefore, enter into His kingdom. Are you in doubt of your salvation? Do you need a physical sign from God that you are truly saved? Then look no further than your Baptism, where you have been cleansed of all your sins and where God has promised you your inheritance of eternal life (Ephesians 1:11-12; Galatians 3:26-27). Also attend the Lord’s Supper, where Christ is truly present and forgives you your sins as a foretaste of the greater Banquet to come in which you shall partake.