The tabernacle as a type of the cosmos, and the timing of John's conception
Chrysostom is arguing that the tabernacle was built as a type of the whole world, and he is about to use the timing of Zechariah's service in the Holy of Holies to establish the date of Christ's birth.
And to show that this is not our own speculation but that the tabernacle was constructed as a type of the whole world, listen to what Paul says when he speaks of Christ ascending into heaven: “For Christ did not enter a holy place made by hands, antitypes of the true ones” (Hebrews 9:24). He shows that the things here were antitypes of the true ones. And that the veil separated the Holy of Holies from the holy places outside, just as this heaven walls off the things above it from all that is here among us—listen to how he hinted at this too, calling heaven a veil. For when he speaks of hope, saying that we have it as an anchor of the soul, sure and firm, he adds: “and entering into the inner side of the veil, where Jesus has entered as a forerunner for us, above the heaven” (Hebrews 6:19-20). Do you see how he called heaven a veil? Outside the veil, then, were the lampstand, the table, and the bronze altar that received the sacrifices and burnt offerings. Inside the veil was the ark, covered all around with gold, holding the tablets of the covenant, the golden jar, and Aaron’s rod that budded, along with a golden altar—not for sacrifices or burnt offerings, but for incense alone. And the outer things all were permitted to walk in, but the inner things only the high priest alone. And of these very things I will again provide testimony, as Paul says in this way: “Now the first tabernacle had regulations for worship, and the worldly holy place” (Hebrews 9:1-2). He calls the outer tabernacle the worldly holy place because the whole world was permitted to enter it. “In it were the lampstand and the table and the presentation of the bread. Behind the second veil was the tabernacle called the Holy of Holies, having a golden censer and the ark of the covenant covered all around with gold, in which was a golden jar holding the manna, and Aaron’s rod that budded, and the tablets of the covenant; and above it were cherubim of glory overshadowing the mercy seat” (Hebrews 9:2-5). Now these things being so arranged, into the first tabernacle the priests entered continually, performing the services; but into the second, once a year, only the high priest alone, not without blood, which he offers for himself and for the ignorances of the people (Hebrews 9:6-7). Do you see that only the high priest enters, and only once in the whole year?
“What does all this have to do with the day before us?” someone says. Wait a little, and do not be troubled. For we are digging the spring from its source, and we are hurrying to reach the very summit, so that everything may become clear to you with ease. Or rather, so that the word may not remain shadowed for long, nor being unclear make you give up at the length of what is said, I will now tell you the reason for which I have stirred up all these things. What then is the reason? When Elizabeth had John in her womb for six months, Mary began to conceive. If therefore we learn which month that sixth month was, we will also know when Mary began to conceive. Then, having learned when she began to conceive, we will also know when she gave birth, counting nine months from the conception.
Greek
Καὶ ὅτι οὐχ ἡμέτερος ταῦτα στοχασμὸς, ἀλλ' ἐν τύπῳ τοῦ κόσμου παντὸς ὁ ναὸς κατεσκεύαστο, ἄκουσον τί φησιν ὁ Παῦλος, περὶ τοῦ Χριστοῦ λέγων εἰς τὸν οὐρανὸν ἀναβάντος· Οὐ γὰρ εἰς χειροποίητα ἅγια εἰσῆλθεν ὁ Χριστὸς, ἀντίτυπα τῶν ἀληθινῶν· δεικνὺς ὅτι τὰ ἐνταῦθα ἀντίτυπα ἦν τῶν ἀληθινῶν. Ὅτι δὲ καὶ τὸ καταπέτασμα διεῖργε τὰ Ἅγια τῶν ἁγίων ἀπὸ τῶν ἁγίων τῶν ἔξω, καθάπερ οὗτος ὁ οὐρανὸς τὰ ὑπὲρ αὐτὸν ἀποτειχίζει τούτων τῶν καθ' ἡμᾶς ἁπάντων, ἄκουσον πῶς καὶ τοῦτο ᾐνίξατο, τὸν οὐρανὸν καταπέτασμα καλέσας. Περὶ γὰρ τῆς ἐλπίδος λέγων, ὅτι ὡς ἄγκυραν αὐτὴν ἔχομεν τῆς ψυχῆς ἀσφαλῆ τε καὶ βεβαίαν, ἐπήγαγε· Καὶ εἰσερχομένην εἰς τὸ ἐσώτερον τοῦ καταπετάσματος, ὅπου πρόδρομος ὑπὲρ ἡμῶν εἰσῆλθεν Ἰησοῦς, ὑπὲρ τὸν οὐρανὸν ἄνω. Ὁρᾷς πῶς καταπέτασμα τὸν οὐρανὸν ἐκάλεσεν; Ἔξω μὲν οὖν τοῦ καταπετάσματος ἦν ἡ λυχνία, καὶ ἡ τράπεζα, καὶ βωμὸς χαλκοῦς, τὰς θυσίας δεχόμενος καὶ τὰ ὁλοκαυτώματα· ἔσω δὲ τοῦ καταπετάσματος ἡ κιβωτὸς, περικεκαλυμμένη πάντοθεν χρυσίῳ, τὰς πλάκας ἔχουσα τῆς διαθήκης, καὶ τὴν στάμνον τὴν χρυσῆν, καὶ τὴν ῥάβδον Ἀαρὼν τὴν βλαστήσασαν, καὶ βωμὸν χρυσοῦν, οὐχὶ θυσιῶν οὐδὲ ὁλοκαυτωμάτων, ἀλλὰ θυμιάματος μόνου. Καὶ τὰ μὲν ἔξω πατεῖν πᾶσιν ἐφεῖτο, τὰ δὲ ἔνδον μόνῳ τῷ ἀρχιερεῖ. Καὶ τούτων δὲ αὐτῶν μαρτυρίαν παρέξομαι πάλιν, τοῦ Παύλου οὕτω πως λέγοντος· Εἶχε μὲν οὖν ἡ πρώτη σκηνὴ δικαιώματα λατρείας, τό τε ἅγιον κοσμικόν. Ἅγιον δὲ κοσμικὸν καλεῖ τὴν ἔξω σκηνὴν, ἐπειδὴ τῷ κόσμῳ παντὶ εἰσιέναι θέμις ἦν· Ἐν ᾗ ἥ τε λυχνία καὶ ἡ τράπεζα καὶ ἡ πρόθεσις τῶν ἄρτων. Μετὰ δὲ τὸ δεύτερον καταπέτασμα σκηνὴ ἡ λεγομένη τὰ Ἅγια τῶν ἁγίων, χρυσοῦν ἔχουσα θυμιατήριον, καὶ τὴν κιβωτὸν τῆς διαθήκης περικεκαλυμμένην πάντοθεν χρυσίῳ· ἐν ᾗ στάμνος χρυσῆ ἔχουσα τὸ μάννα, καὶ ἡ ῥάβδος Ἀαρὼν ἡ βλαστήσασα, καὶ αἱ πλάκες τῆς διαθήκης· ὑπεράνω δὲ αὐτῆς Χερουβὶμ δόξης, κατασκιάζοντα τὸ ἱλαστήριον. Τούτων δὲ οὕτω κατεσκευασμένων, εἰς μὲν τὴν πρώτην σκηνὴν διαπαντὸς εἰσίασιν οἱ ἱερεῖς, τὰς λατρείας ἐπιτελοῦντες· εἰς δὲ τὴν δευτέραν ἅπαξ τοῦ ἐνιαυτοῦ μόνος ὁ ἀρχιερεὺς, οὐ χωρὶς αἵματος, ὃ προσφέρει ὑπὲρ ἑαυτοῦ καὶ τῶν τοῦ λαοῦ ἀγνοημάτων. Ὁρᾷς ὅτι καὶ μόνος εἰσέρχεται ὁ ἀρχιερεὺς, καὶ ἅπαξ τοῦ ἐνιαυτοῦ παντός; δʹ. Τί οὖν ταῦτα, φησὶ, πρὸς τὴν προκειμένην ἡμέραν; Ἀναμείνατε μικρὸν, καὶ μὴ θορυβεῖσθε. Ἄνωθεν γὰρ τὴν πηγὴν διορύττομεν, καὶ ἐπ' αὐτὴν σπεύδομεν τὴν κορυφὴν ἐλθεῖν, ὥστε μετ' εὐκολίας ὑμῖν ἅπαντα γενέσθαι δῆλα· μᾶλλον δὲ, ἵνα μὴ μέχρι πολλοῦ ὁ λόγος συνεσκιασμένος ᾖ, μηδὲ ἀσαφέστερος ὢν ἀπαγορεύειν ὑμᾶς ποιήσῃ πρὸς τὸ μῆκος τῶν λεγομένων, ἤδη τὴν αἰτίαν ὑμῖν ἐρῶ, δι' ἣν ταῦτα πάντα ἀνεκίνησα. Τίς οὖν ἐστιν ἡ αἰτία; Ἓξ μῆνας ἐν γαστρὶ ἐχούσης τῆς Ἐλισάβετ τὸν Ἰωάννην, ἡ Μαρία ἤρξατο συλλαμβάνειν. Ἂν τοίνυν μάθωμεν ποῖος ἐκεῖνος ὁ μὴν ὁ ἕκτος ἦν, εἰσόμεθα καὶ πότε ἤρξατο συλλαμβάνειν ἡ Μαρία· εἶτα μαθόντες, πότε ἤρξατο συλλαμβάνειν, εἰσόμεθα καὶ πότε ἔτεκεν, ἐννέα μῆνας ἀριθμήσαντες ἐκ τῆς συλλήψεως.