A frequent prayer in the Bible is for the strength that we need and that God alone can give. It is in the Old Testament as in Deuteronomy 33:25, "as your days, so may your strength be." We have Samson' prayer for strength (Jud.16:28), and in 1 Samuel 30:6 it says that "David strengthened himself in the Lord his God." Elijah sought a demonstration of the power of the Lord in the face of the claims of the prophets of Baal, and his prayer on Mt. Carmel was answered (1 Kings 18). We read in Nehemiah 6:9 of the way that Nehemiah, faced with a dangerous and difficult task, and fearing that the hands of his people would "drop from the work" of rebuilding the wall of Jerusalem, prayed "O God, strengthen my hands". The deep sense of human weakness and need prompted the prayer of Isaiah 64:1 for the power of God to break into human life, "O that you would tear open the heavens and come down, so that the mountains would quake at your presence --- so that the nations might tremble at your presence!"
There are many prayers for strength in the New Testament. The prayer of Ephesians 1:19-22 is that Paul's readers may know "what is the immeasurable greatness of his power for us who believe, according to the working of his great power. God put this power to work in Christ when he raised him from the dead and seated him at his right hand in the heavenly places, far above all rule and authority and power and dominion --- and he has put all things under his feet ---." In the later prayer in Ephesians 3:16 he says, "I pray that, according to the riches of his glory, he may grant that you may be strengthened in your inner being with power through his Spirit --." In 2 Thessalonians 1:11 his prayer is "that our God will make you worthy of his call and will fulfil by his power every good resolve and work of faith, so that the name of our Lord Jesus may be glorified in you --." Again in that same epistle Paul prays, "Now may our Lord Jesus Christ himself and God our Father, who loved us and through grace gave us eternal comfort and good hope, comfort your hearts and strengthen them in every good work and word" (2 Thess.2:16-17)
The prayer for strength is often essentially a prayer for courage and boldness. In the Old Testament it is often the request that one may not be ashamed in the face of those who have no regard for God (e.g.Ps.25:2, 119:80 and Jer.17:14-18). So in the New Testament we often hear Christians praying for boldness in the face of those who oppose or mock the Christ whom they serve. We have noted the way that in Acts 4:29 the early Christians prayed at a time when persecution threatened, and in their prayer there was no request that opposition might cease or that the way might be made easier, but "Lord, look at their threats and grant to your servants to speak your word with all boldness." The apostle Paul similarly asked his fellow-Christians to pray that he would have that boldness in proclaiming the message of Christ (Eph. 6:19, Phil.1:20).