After Hezekiah received this miraculous deliverance, he became mortally ill. Isaiah came to him and said, "Thus says Jehovah, Put your house in order, for you are about to die and will not live" (38:1). Then Hezekiah again prayed a very godly prayer, saying, "O Jehovah, please remember how I have walked before You in truth, with a perfect heart, and have done that which is good in Your sight" (v. 3). God heard Hezekiah's prayer and answered it by healing him and saying, through Isaiah, that He would add fifteen years to his life (vv. 4-5).
The number of years added to Hezekiah's life is significant. When Hezekiah became mortally ill, he was a middle-aged man, perhaps about forty years old. For God to give him another fifteen years meant that he would live until the age of approximately fifty-five. Since God was willing to heal Hezekiah, why did He not give him another thirty years and allow him to reach the age of seventy? I believe that the reason God extended Hezekiah's life by only fifteen years was that, in the sight of God, Hezekiah was not a person who could be trusted to carry out God's purpose. Had Hezekiah been permitted to live longer, he might have caused even more trouble to God's kingdom than he did in chapter thirty-nine. During his last fifteen years, Hezekiah made a mistake that was so serious that it caused God's kingdom on earth to be lost.
Isaiah 39 shows us that instead of being a considerate and careful person, Hezekiah was hasty. His prayers indicated that he had a sober mind and was quite wise. However, after he was healed by God, he did something foolish when visitors from Babylon came to him with a gift. Receiving the gift, he showed the visitors his treasury, his whole armory, and everything in his dominion (v. 2). This was a foolish act and a great mistake. The showing of these riches, which had been accumulated by his fathers since the time of David and Solomon, became a temptation to the king of Babylon. A little over one hundred years later, the king of Babylon came and took away these riches. Hezekiah did not consider his action carefully, nor did he pray about it. He should have been careful, knowing that Babylon was Judah's enemy and that sooner or later the Babylonian army would come to destroy him. However, Hezekiah did not take thought concerning what the king of Babylon might do. This shows that Hezekiah was hasty and not very considerate or careful.