Fasting was used by the saints during times of tribulations.
We have a very clear example of that in the fasting of Esther and all the Jews when they were confronted by Haman’s conspiracy (Esther 4:16), and the Lord’s response was quick and amazing. We also hear about the fasting of Nehemiah when he heard the news that: “The wall of Jerusalem is also broken down and its gates are burned with fire” (Neh 1:3,4). The book of Nehemiah also tells about the Lord’s response and how it was quick and amazing... The Bible also tells us about how Ezra and Hobak fasted and the effect it had on cleansing and purifying the people. The Bible also tells us about the fasting of the Prophet Daniel and its effect (Dan 9:3,21) and (Dan 10:3,12).