'Incredulous' in the Bible

It is he who will go as a forerunner before Him in the spirit and power of Elijah, to turn the hearts of the fathers back to the children, and the disobedient to the attitude of the righteous [which is to seek and submit to the will of God]—in order to make ready a people [perfectly] prepared [spiritually and morally] for the Lord.”

Then He said to Thomas, “Reach here with your finger, and see My hands; and put out your hand and place it in My side. Do not be unbelieving, but [stop doubting and] believe.”