In those days. Hebrew idiom for an indefinite time (Exo_2:11, Exo_2:23. Isa_38:1, &c): while the Lord, being grown up, was still dwelling in Nazareth. App-169. Compare Mat_2:23.
came. Greek comes: i.e. presenteth himself.
came John, &c. Because "the word of God" had come to him (Luk_3:2).
John the Baptist = John the baptizer.
preaching = proclaiming as a herald. App-121.
in. Greek. en.App-104.
wilderness = country parts, which were not without towns or villages. David passed much of his time there. So John, probably in some occupation also; John now thirty years old. He was the last and greatest of the prophets, and would have been reckoned as Elijah himself, or as an Elijah (Mat_11:14. Compare Mal_3:1; Mal_4:5) had the nation obeyed his proclamation.