Matthew Poole and continuators on Jonah 3:4

4 And Jonah began to enter into the city a days journey, and he cryed, and said , Yet forty days and Nineveh shall be overthrown .

The former verse gives us intelligence of Ionah's arrival at Nineveh; now, so soon as come, he preacheth.

To walk through and to preach the dreadful threats of God against Nineveh, and he proclaimed openly and plainly what God commanded; he feared not to tell all what concerned all, he did it with earnestness as deeply affected with what he spake from God against this mighty City.

A very short time, some might think, for this great City, but 'tis more time then God was bound to give, or then they could deserve, or then God gave to Sodom and Gomorrah, the sins of which Cities were no doubt found in Nineveh now Ionah preached, and grew ripe by that time Nahum came to foretell their ruine, vid. Nahum tot. the threat is express and peremptory in its form and words; though there be a reserve with God on condition of Repentance which operated in due time, and manifestly proved that God intended mercy to repenting Nineveh, though he threatned an overthrow to impenitent Nineveh, how it should be overthrown is not expressed, some conjecture by a forreign Enemy, which carrieth unlikelihood with it, others guesse by fire from Heaven, but since 'twas not destroyed we need not enquire how it should have been, and had they not repented the event would have informed us fully.