Prayer/Promise
God's Word is a record of prayer - of praying men and their achievements of the divine warrant of prayer, and of the encouragement given to those who pray. No one can read the instances, commands, and examples of statements that concern themselves with prayer without realizing that the cause of God and the success of His work in this world are committed to prayer. Praying men have been God's appointed officers on earth. Those men who do not pray have never been used by Him.
A reverence for God's holy name is closely related to a high regard for His Word. The hallowing of God's name, the ability to do His will on earth as it is done in heaven, and the establishment and glory of God's kingdom are as much involved in prayer as when Jesus taught men the universal prayer. That "men ought always to pray, and not to faint" is as fundamental to God's cause today as when Jesus Christ enshrined that great truth in the immortal setting of the parable of the persistent widow (Luke 18:1).
As God's house is called the house of prayer because prayer is the most important of its holy offices, so by the same token, the Bible may be called the book of prayer. Prayer is the great theme and content of it's message to mankind.
As the Word of God is the support upon which the lever of prayer is placed and by which things are mightily moved. God has committed Himself, His purpose, and His promise to prayer. His Word becomes the basis and the inspiration of our praying. In certain circumstances, persistent prayer may yield additional assurance of His promises.