For a while now, I've been slowly working my way through Martin Luther's Lectures on Genesis. Reading Luther is... an interesting adventure, let's say. Last night I reached a section in which Luther went off on a tangent about the nature of allegory and presented a model allegory that he deemed acceptable under the rule of faith; he presented a treatment of the release of various birds by Noah from the ark. I'd like to summarize, briefly, what it is that Luther said, but first, here's that passage as a refresher:
And it came to pass at the end of forty days, that Noah opened the window of the ark which he had made: and he sent forth a raven, which went to and fro, until the waters were dried up from off the earth. Also he sent forth a dove from him, to see if the waters were abated from off the face of the ground; but the dove found no rest for the sole of her foot, and she returned unto him into the ark, for the waters were on the face of the whole earth: then he put forth his hand, and took her, and pulled her in unto him into the ark. And he stayed yet other seven days, and again he sent forth the dove out of the ark; and the dove came in to him in the evening; and, lo, in her mouth was an olive leaf pluckt off: so Noah knew that the waters were abated from off the earth. And he stayed yet other seven days; and sent forth the dove; which returned not again unto him any more. (Genesis 8:6-12)
Luther says that the raven signifies a teacher of the law, or of works-righteousness, which has indeed been sent out by God but cannot return to him with a message of reconciliation between God and man because the law is a 'ministry of death' (cf. Romans 7:9). The first mission of the dove, then, represents the ministry of the prophets who prepared the way for Christ. They still ministered during the era of the law (represented here by the continued presence of the waters of the flood), but they were able to preach the need for faith in the coming Blessed Seed. The second mission of the dove represents the ministry of the New Covenant, which in its mouth - signifying the ministry of the preached word of God - can indeed bring back an olive branch/leaf of redemption. The green of the leaf/branch signifies the fact that the message of the gospel is permanent and enduring and is never without fruit. So what, then, of the third dove? Luther says:
The third dove did not return. When the promise of the Gospel, announced to the world through the mouth of a dove, has been fulfilled, there is nothing left to do, and no new doctrine is expected. All we still expect is the revelation of the things we have believed. Hence this also serves to give us a sure testimony that this doctrine will endure until the end of the world. (LW 2:163)
Now that the 'knowledge of the Blessed Seed' has been revealed, "there is nothing left except the revelation of what we believe and our flight with the third dove into another life" (LW 2:164). Hence, after the New Testament, there is no further revelation of that sort from God, only revelation such as confirms the faith that had already been delivered completely to the people of God (cf. Jude 3). Such, at least, is Luther's allegory of the birds released from the ark.