<Genesis 18>, where Abraham speaks to God on behalf of Sodom.

Ezek 22:30 And I sought for a man among them, that should make up the hedge, and stand in the gap before me for the land, that I should not destroy it: but I found none.

Exod 17:8-13 Then Amalek came and fought against Israel at Rephidim.
9 So Moses said to Joshua, "Choose men for us, and go out, fight against Amalek. Tomorrow I will station myself on the top of the hill with the staff of God in my hand."
10 And Joshua did as Moses told him, and fought against Amalek; and Moses, Aaron, and Hur went up to the top of the hill.
11 So it came about when Moses held his hand up, that Israel prevailed, and when he let his hand down, Amalek prevailed.
12 But Moses' hands were heavy. Then they took a stone and put it under him, and he sat on it; and Aaron and Hur supported his hands, one on one side and one on the other. Thus his hands were steady until the sun set.
13 So Joshua overwhelmed Amalek and his people with the edge of the sword.

Acts 12:1-17 Now about that time Herod the king stretched out his hand to harass some from the church.
2 Then he killed James the brother of John with the sword.
3 And because he saw that it pleased the Jews, he proceeded further to seize Peter also. Now it was during the Days of Unleavened Bread.
4 So when he had apprehended him, he put him in prison, and delivered him to four squads of soldiers to keep him, intending to bring him before the people after Passover.
5 Peter was therefore kept in prison, but constant prayer was offered to God for him by the church.
6 And when Herod was about to bring him out, that night Peter was sleeping, bound with two chains between two soldiers; and the guards before the door were keeping the prison.
7 Now behold, an angel of the Lord stood by him, and a light shone in the prison; and he struck Peter on the side and raised him up, saying, "Arise quickly!" And his chains fell off his hands.
8 Then the angel said to him, "Gird yourself and tie on your sandals"; and so he did. And he said to him, "Put on your garment and follow me."
9 So he went out and followed him, and did not know that what was done by the angel was real, but thought he was seeing a vision.
10 When they were past the first and the second guard posts, they came to the iron gate that leads to the city, which opened to them of its own accord; and they went out and went down one street, and immediately the angel departed from him.
11 And when Peter had come to himself, he said, "Now I know for certain that the Lord has sent His angel, and has delivered me from the hand of Herod and from all the expectation of the Jewish people."
12 So, when he had considered this, he came to the house of Mary, the mother of John whose surname was Mark, where many were gathered together praying.
13 And as Peter knocked at the door of the gate, a girl named Rhoda came to answer.
14 When she recognized Peter's voice, because of her gladness she did not open the gate, but ran in and announced that Peter stood before the gate.
15 But they said to her, "You are beside yourself!" Yet she kept insisting that it was so. So they said, "It is his angel."
16 Now Peter continued knocking; and when they opened the door and saw him, they were astonished.
17 But motioning to them with his hand to keep silent, he declared to them how the Lord had brought him out of the prison. And he said, "Go, tell these things to James and to the brethren." And he departed and went to another place.

Eph 6:18-20 praying always with all prayer and supplication in the Spirit, being watchful to this end with all perseverance and supplication for all the saints--
19 and for me, that utterance may be given to me, that I may open my mouth boldly to make known the mystery of the gospel,
20 for which I am an ambassador in chains; that in it I may speak boldly, as I ought to speak.

Col 4:2-4 Continue earnestly in prayer, being vigilant in it with thanksgiving;
3 meanwhile praying also for us, that God would open to us a door for the word, to speak the mystery of Christ, for which I am also in chains,
4 that I may make it manifest, as I ought to speak.

Col 4:12 Epaphras, who is one of you, a bondservant of Christ, greets you, always laboring fervently for you in prayers, that you may stand perfect and complete in all the will of God.

1 Sam 12:23 "Moreover, as for me, far be it from me that I should sin against the LORD in ceasing to pray for you; but I will teach you the good and the right way