Did Noah Warn People About the Coming Flood?

We know that Noah was described as a preacher (or herald) of righteousness (2 Peter:2:5And spared not the old world, but saved Noah the eighth person, a preacher of righteousness, bringing in the flood upon the world of the ungodly;
See All...), and that the act of preparing the ark was a witness in and of itself of coming judgment. Especially since Hebrews:11:7By faith Noah, being warned of God of things not seen as yet, moved with fear, prepared an ark to the saving of his house; by the which he condemned the world, and became heir of the righteousness which is by faith.
See All... states: “By faith Noah, being warned by God concerning events as yet unseen, in reverent fear constructed an ark for the saving of his household. By this he condemned the world and became an heir of the righteousness that comes by faith.”

However, Scripture often indicates that even if no one repented, this would not have absolved Noah of warning people about the coming judgment. Think of Jeremiah who preached to Judah for 40 years and apparently only his scribe Baruch and a court eunuch Ebed-melech the Ethiopian (likely a title “the king’s eunuch” rather than a personal name, Jeremiah 38) listened to his call for repentance. Ebed-melech heard the Word of the Lord and repented and became a true believer/follower of God (Jeremiah:39:16Go and speak to Ebedmelech the Ethiopian, saying, Thus saith the LORD of hosts, the God of Israel; Behold, I will bring my words upon this city for evil, and not for good; and they shall be accomplished in that day before thee.
See All...–18). In this regard, Jeremiah and Noah are both alike—they were “preachers of righteousness” who ended up having a “ministry of condemnation.” Jeremiah even complained that he did not want to preach “disaster,” but God compelled him with anguish if he did not (Jeremiah:20:8For since I spake, I cried out, I cried violence and spoil; because the word of the LORD was made a reproach unto me, and a derision, daily.
See All...–9).

Furthermore, even though we do not know whether God ever directly communicated a need to Noah to warn the people of his day about the coming flood, it would be consistent with other biblical examples. Think of Ezekiel who was told by God that he was required to warn people of divine judgment.

“So, you, son of man, I have made a watchman for the house of Israel. Whenever you hear a word from my mouth, you shall give them warning from me. If I say to the wicked, O wicked one, you shall surely die, and you do not speak to warn the wicked to turn from his way, that wicked person shall die in his iniquity, but his blood I will require at your hand. But if you warn the wicked to turn from his way, and he does not turn from his way, that person shall die in his iniquity, but you will have delivered your soul” (Ezekiel:33:7So thou, O son of man, I have set thee a watchman unto the house of Israel; therefore thou shalt hear the word at my mouth, and warn them from me.
See All...–9).

Therefore, the pattern in Scripture of someone blessed with divine forewarnings of judgment is that they felt burdened (or directly commanded) by the Lord to share that message and were told they would suffer (or suffer blame) if they did not. It is entirely consistent then to believe Noah was under the same burden to warn people of coming judgment. However, since we are not directly told one way or the other, we can only make biblically based hypotheses on this subject and not dogmatic proclamations. 

Hypothetically, if the whole world believed Noah and repented, God would not have needed to send the flood as a judgment against the world’s wickedness. We see similar instances of God relenting from promised punishment in that he would have spared Sodom for as few as 10 righteous men, and he did not destroy Nineveh when they repented. Additionally, the ark had plenty of extra room if only a few had repented. However, whenever we deal with hypotheticals, especially when we have limited data, we are on shaky ground. What we do know is that the ark had plenty of room for many who would have believed and all the animals Noah was commanded to bring on board.

It appears that there is a twofold answer to this question of others outside of Noah’s family boarding the ark. The size of the ark was such that it could have accommodated thousands more people.

However, we need to recall that based on the prophecy given in Genesis:6:13And God said unto Noah, The end of all flesh is come before me; for the earth is filled with violence through them; and, behold, I will destroy them with the earth.
See All...–22 (specifically verse 18) obviously given to Noah before the ark was built, God had said that Noah and his family only would be saved: “But I will establish my covenant with you, and you shall come into the ark, you, your sons, your wife, and your sons’ wives with you.” Since God is omniscient, he knew that mankind would continue in their wickedness and refuse to board (or even acknowledge) the ark. God also knew that the few righteous people (like Methuselah) would die before the flood came.

It appears from the size of the ark and its excess capacity that God may have wanted Noah to prepare for and see how many more could have been on the ark, but God knew that the space would not be used for that purpose. However, we cannot know this for sure based on Scripture alone….But in any event, Noah knew that it was not “lack of space” that kept people off the ark—it was their own love of sin and unbelief in God (and God’s holiness in judging his creatures). So, the answer to this question is that it appears that God did not directly invite anyone but Noah and his family aboard the ark. And as far as Noah knew, he and his immediate family members would be the only humans on board (per Genesis:6:18But with thee will I establish my covenant; and thou shalt come into the ark, thou, and thy sons, and thy wife, and thy sons' wives with thee.
See All...). Had someone repented and believed Noah though, God could have extended the invitation to them; however, God already knew this would not happen. I know this thought process seems antithetical, yet man’s responsibility and God’s sovereignty and omniscience are not mutually exclusive. God is sovereign, and yet, man is responsible. Had there been someone who repented, God could have told Noah that his family and others would board the ark with Noah’s family.

Noah knew that it was not “lack of space” that kept people off the ark—it was their own love of sin and unbelief in God (and God’s holiness in judging his creatures).

Some have objected to this based on Genesis:6:13And God said unto Noah, The end of all flesh is come before me; for the earth is filled with violence through them; and, behold, I will destroy them with the earth.
See All... and 17 where God promises to destroy all flesh on the earth. But it is possible that this also would have served a dual purpose; divine condemnation for those who ignored the warning but perhaps also repentance for those who may have been older and died before the flood came or for those who repented at the time of the flood. God can certainly relent from punishing repentant sinners, as seen with Nineveh in Jonah’s time.

But also consider Numbers:14:11And the LORD said unto Moses, How long will this people provoke me? and how long will it be ere they believe me, for all the signs which I have shewed among them?
See All...–12 (recounted by Moses in Deuteronomy 9) where God tells Moses that he will destroy the Israelites because of their continued rebellion, yet Moses pleaded with God on this occasion (and several others), and God lessened his punishment only to immediately punish the 10 unbelieving spies and eventually all the Israelites over 40 years old (Numbers:14:29Your carcases shall fall in this wilderness; and all that were numbered of you, according to your whole number, from twenty years old and upward, which have murmured against me,
See All...). God can and does change the parameters of his just punishments when he wishes to extend mercy. There is no greater example of this in Scripture than Christ’s death on the cross, the just for the unjust (Romans:5:6For when we were yet without strength, in due time Christ died for the ungodly.
See All...–10; Ephesians:2:12That at that time ye were without Christ, being aliens from the commonwealth of Israel, and strangers from the covenants of promise, having no hope, and without God in the world:
See All...–13; 1 Peter:3:18For Christ also hath once suffered for sins, the just for the unjust, that he might bring us to God, being put to death in the flesh, but quickened by the Spirit:
See All...).

https://answersingenesis.org/the-flood/did-noah-warn-people-about-coming-flood/