Jonah 3:4

“And Jonah began to enter into the city a day’s journey, etc.] As soon as he came to it, he did not go into an inn, to refresh himself after his wearisome journey; or spend his time in gazing upon the city, and to observe its structure, and the curiosities of it; but immediately sets about his work, and proclaims what he was bid to do; and before he could finish one day’s journey, he had no need to proceed any further, the whole city was alarmed with his preaching, was terrified with it, and brought to repentance by it: and he cried; as he went along; he lifted up his voice like a trumpet, that everyone might hear; he did not mutter it out, as if afraid to deliver his message, but cried aloud…”

“a day's journey--not going straight forward without stopping: for the city was but eighteen miles in length; but stopping in his progress from time to time to announce his message to the crowds gathering about him. Yet forty days, and Nineveh shall be overthrown--The commission, given indefinitely at his setting out, assumes now on his arrival a definite form, and that severer than before. It is no longer a cry against the sins of Nineveh, but an announcement of its ruin in forty days. This number is in Scripture associated often with humiliation. It was forty days that Moses, Elijah, and Christ fasted. Forty years elapsed from the beginning of Christ's ministry (the antitype of Jonah's) to…”

“And Jonah began to enter the city a day’s journey - Perhaps the day’s journey enabled him to traverse the city from end to end, with his one brief, deep cry of woe; “Yet forty days and Nineveh overthrown.” He prophesied an utter overthrow, a turning it upside down. He does not speak of it as to happen at a time beyond those days. The close of the forty days and the destruction were to be one. He does not say strictly, “Yet forty days and Nineveh shall be overthrown,” but, “Yet forty days and Nineveh overthrown.” The last of those forty days was, ere its sun was set, to see Nineveh as a “thing overthrown.” Jonah knew from the first God’s purpose of mercy to Nineveh; he had a further hint of…”

“Shall be overthrown - The threat is express. But there was a reserve with God, on condition of repentance. Jonah 3:5”

“3:4 Forty days from now Nineveh will be destroyed! Jonah’s message apparently did not include a contingency clause—e.g., “But if you repent, God will not destroy you” (note the king’s uncertainty in 3:9). Jonah knew, however, of God’s desire for people to repent rather than be destroyed (3:10; 4:2).”

“Yet: Jon 3:10; Deu 18:22; Kg2 20:1, Kg2 20:6; Jer 18:7-10 Jonah 3:5”