Quanti abitanti aveva Babilonia all'epoca della predicazione di Pietro?
Non lo sappiamo con precisione, ma è certo che nel I secolo a Babilonia (nome che potrebbe anche indicare alcune delle borgate attorno alla città) vi era una numerosa e prospera comunità giudaica, probabilmente una delle più importanti con Alessandria e Roma. Questo giustificherebbe la presenza di Pietro a cui era stata in particolare affidata l'evangelizzazione ai giudei.
Sui dettagli storici puoi consultare la Jewish Encyclopedia:
"Xerxes is said to have either plundered or destroyed the temple of Belus, and Alexander the Great labored in vain to restore it; in connection with this, reference is made to his Jewish soldiers (see Babylonia, Greek Period). When Seleucus Nicator founded Seleucia for his capital, Babylon sank in importance and soon fell into ruins (Pausanias, viii. 33, 1; Dio Cassius, lxxv. 9). The Rabbis nevertheless still knew it as a city. Mention is made of baskets taken to Babylon (B. B. 22a), as also of the fact that one could live as well in Babylon as in Sura (Giṭ. 65a). The Talmud says, "He who sees the Euphrates from the bridge near Babylon, should say the benediction, 'Blessed be the Creator of nature'" (Ber. 59b), meaning that from Babylon the Euphrates has a natural course, being checked further north by artificial dams and canals. This is the probable explanation of the passage, although there is another view, held by S. Cassel, who thinks that the land of Babylonia is meant here and not the city of Babylon. To the foregoing precept the Talmud adds —from a fifth-century point of view—that since even at this point the river had been checked by artificial means, the benediction could properly be said only lower down the stream, in Be Shabur. R. Hamnuna preached that "He who beholds the godless city of Babylon should pronounce five benedictions; the first, on sighting the ruins of the town; the second, when he beholds the house of Nebuchadnezzar; the third, when he sees Daniel's den of lions; the fourth, when he looks on the fiery furnace; and the fifth, when before the pillars of Mercury" (ib. 57b; less correctly, in Yer. Ber. ix. 12d). The palace of Nebuchadnezzar is a heap of ruins called by the Arabs "El Ḳaṣr" (the palace); the "pillars of Mercury" are probably a statue of the god Nebo; the "fiery furnace" is shown next to "the palace" (Layard, "Discoveries," p. 505). Benjamin of Tudela found the ruins of Babylon five miles distant from Hillah, a city which then contained ten thousand Jews. In thework "Shebile 'Olam," i. 25a., Hillah is incorrectly identified with Babylon. Pethahiah also saw ancient Babylon (ed. London, pp. 42-44); he, however, often seems to confuse Babylon with Bagdad, as do many Jewish authors. Of older date is its confusion with Borsippa, an error of ancient times (Yoma 10a); the latter place did indeed possess a temple of Nebo ('Ab. Zarah 11b). An aged pine-tree was shown in the vicinity (Sanh. 92b), which served to locate events in the time of Daniel (see Rapoport, "'Erek Millin," 241b). Jews looked for the Tower of Babel in Babylon (compare Sanh. 109a): "Of the tower [of Babel], one-third was burnt, one-third was buried underground, and one-third remains standing" (see "Proc. Soc. Bibl. Archæol.," 1893, xv. 230). Pethahiah also saw the Tower (l.c. p. 48).
Christians lived in Babylon in early times; the passage I Peter v. 13 refers to this (compare Josephus, "Ant." xv. 2, § 2). A Christian church, said to have been destroyed by Jews under Sapor II. or Bahram, was restored in 399 (Assemani, "Bibl. Orientalis," iii. 2, 61)".
Shalom