When people hear that God’s covenant with us in Christ is conditional they sometimes act like you’re trying to scare them. Yes, some aspects can be frightening. For example:
Then a man of God came to Eli and said to him, “Thus says the LORD, ‘Did I not indeed reveal Myself to the house of your father when they were in Egypt in bondage to Pharaoh’s house? Did I not choose them from all the tribes of Israel to be My priests, to go up to My altar, to burn incense, to carry an ephod before Me; and did I not give to the house of your father all the fire offerings of the sons of Israel? Why do you kick at My sacrifice and at My offering which I have commanded in My dwelling, and honor your sons above Me, by making yourselves fat with the choicest of every offering of My people Israel?’ Therefore the LORD God of Israel declares, ‘I did indeed say that your house and the house of your father should walk before Me forever’; but now the LORD declares, ‘Far be it from Me–for those who honor Me I will honor, and those who despise Me will be lightly esteemed. Behold, the days are coming when I will break your strength and the strength of your father’s house so that there will not be an old man in your house. You will see the distress of My dwelling, in spite of all the good that I do for Israel; and an old man will not be in your house forever. Yet I will not cut off every man of yours from My altar so that your eyes will fail from weeping and your soul grieve, and all the increase of your house will die in the prime of life. This will be the sign to you which will come concerning your two sons, Hophni and Phinehas: on the same day both of them will die. But I will raise up for Myself a faithful priest who will do according to what is in My heart and in My soul; and I will build him an enduring house, and he will walk before My anointed always. Everyone who is left in your house will come and bow down to him for a piece of silver or a loaf of bread and say, “Please assign me to one of the priest’s offices so that I may eat a piece of bread”‘” (First Samuel 2.27-36).
So here God made a promises and now recants it. Eli doesn’t get to keep the privileges God promised him because he has violated the terms of God’s covenant. As I said: frightening. But there is another aspect that needs to be considered:
Now the word of the LORD came to Jonah the second time, saying, “Arise, go to Nineveh the great city and proclaim to it the proclamation which I am going to tell you.” So Jonah arose and went to Nineveh according to the word of the LORD. Now Nineveh was an exceedingly great city, a three days’ walk. Then Jonah began to go through the city one day’s walk; and he cried out and said, “Yet forty days and Nineveh will be overthrown.” Then the people of Nineveh believed in God; and they called a fast and put on sackcloth from the greatest to the least of them. When the word reached the king of Nineveh, he arose from his throne, laid aside his robe from him, covered himself with sackcloth and sat on the ashes. He issued a proclamation and it said, “In Nineveh by the decree of the king and his nobles: Do not let man, beast, herd, or flock taste a thing. Do not let them eat or drink water. But both man and beast must be covered with sackcloth; and let men call on God earnestly that each may turn from his wicked way and from the violence which is in his hands. Who knows, God may turn and relent and withdraw His burning anger so that we will not perish.” When God saw their deeds, that they turned from their wicked way, then God relented concerning the calamity which He had declared He would bring upon them. And He did not do it (Jonah 3).
God’s declaration through Jonah was that, in forty days, they would all be corpses. He doesn’t say that the destruction will come if they continue in sin or unless they repent, but nevertheless, the judgment is conditional. They repent and God spares them.
Would anyone have it any other way?
The condition, ultimately, comes down to faith. Eli showed an unbelieving attitude by his behavior (though I trust not entirely so). The king and people of Ninevah believed God by believing Jonah’s message.