God preserved a whole nation because they were willing to do what He asked them to do:
For Ezra had prepared his heart to seek the law of the LORD, and to do it, and to teach in Israel statutes and judgments. Ezra 7:10
Then I proclaimed a fast there, at the river of Ahava, that we might afflict ourselves before our God, to seek of him a right way for us, and for our little ones, and for all our substance. Ezra 8:21
The hand of our God is upon all them for good that seek him; but his power and his wrath is against all them that forsake him. Ezra 8:22b
The hand of our God is upon all them for good that seek him; but his power and his wrath is against all them that forsake him. Ezra 8:31
And at the evening sacrifice I arose up from my heaviness; and having rent my garment and my mantle, I fell upon my knees, and spread out my hands unto the LORD my God Ezra 9:5
And now for a little space grace hath been shewed from the LORD our God, to leave us a remnant to escape, and to give us a nail in his holy place, that our God may lighten our eyes, and give us a little reviving in our bondage. Ezra 9:8
But this people hath a revolting and a rebellious heart; they are revolted and gone. Neither say they in their heart, Let us now fear the LORD our God, that giveth rain, both the former and the latter, in his season: he reserveth unto us the appointed weeks of the harvest. For among my people are found wicked men: they lay wait, as he that setteth snares; they set a trap, they catch men. Jeremiah 5:23-24, 26
For if thou altogether holdest thy peace at this time, then shall there enlargement and deliverance arise to the Jews from another place; but thou and thy father's house shall be destroyed: and who knoweth whether thou art come to the kingdom for such a time as this? Then Esther bade them return Mordecai this answer, Go, gather together all the Jews that are present in Shushan, and fast ye for me, and neither eat nor drink three days, night or day: I also and my maidens will fast likewise; and so will I go in unto the king, which is not according to the law: and if I perish, I perish. Esther 4:14-16
And it was so, when the king saw Esther the queen standing in the court, that she obtained favour in his sight: and the king held out to Esther the golden sceptre that was in his hand. So Esther drew near, and touched the top of the sceptre.