And GOD saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of his heart was only evil continually. And it repented the LORD that He had made man on the earth, and it grieved Him at His heart. And the LORD said, I will destroy man whom I have created from the face of the earth; both man, and beast, and the creeping thing, and the fowls of the air; for it repenteth Me that I have made them. But Noah found grace in the eyes of the LORD. (Gen 6:5-8)
GOD shut that door, when it was obvious that no one would come in faith, believing GOD's Word at the preaching of Noah, and they were destroyed. GOD is merciful, but GOD is also holy and just. Man is just as depraved and unholy, apart from GOD, as he was in those days, and since GOD promised He would not flood the earth again, the next judgment is by fire. It is already proclaimed, the timing is the Lord's, but it will come and when it does there will be no more mercy for those who have rejected the grace of GOD through the open door of Jesus Christ and His finished and perfect work on the Cross of Calvary.
Until that day, we who know GOD through faith in Him, are commanded to tell everyone we meet of His mercy, judgment, grace and holiness. We are to minister to the hurting as GOD gives the increase, we are to disciple one another in love and His Word, and as we go, we are to proclaim the Good News of Jesus Christ and the forgiveness of sIn and Salvation that GOD offers to those that believe and believing have life in His Name.
For GOD is not willing that any should perish, but that all would come to repentance and the knowledge of the Truth. Jesus loves you and wants to establish a covenant relationship with you that is real and personal. Surrender to Him on His terms and trust Him for Salvation and He will give you a brand new life of discipleship and fellowship with Him that is abundant and everlasting. GOD is holding the door open, but there will come a day that He shuts it, just as He did with the ark. Believe His Word and receive Him by faith in what He has already done on that cruel Roman cross today.