What is the power of Prayer? What can prayers do? 

1) Strengthen your Relationship with God

God is our father. A father-child relationship can be strengthened by frequent conversations.

Matthew 6:9-13 - After this manner therefore pray ye: Our Father which art in heaven, Hallowed be thy name. 

2) Overcome Evil

Matthew 26:41 - Watch and pray, that ye enter not into temptation: the spirit indeed [is] willing, but the flesh [is] weak.

3) Change your circumstances

There is no guarantee that prayer will always change your circumstance the way you want. But, there is always a possibilty. God can do anything He wants to and there is nothing impossible for Him.

Jeremiah 33:3 - Call unto me, and I will answer thee, and shew thee great and mighty things, which thou knowest not.

Psalms 34:17 - [The righteous] cry, and the LORD heareth, and delivereth them out of all their troubles.

John 15:7 - If ye abide in me, and my words abide in you, ye shall ask what ye will, and it shall be done unto you.

4) Reverse the Consequences of your sinful disobedience

2 Chronicles 7:14 

“If my people, which are called by my name, shall humble themselves, and pray, and seek my face, and turn from their wicked ways; then will I hear from heaven, and will forgive their sin, and will heal their land.”

5) Eternal Rewards

Matthew 16:27 - For the Son of man shall come in the glory of his Father with his angels; and then he shall reward every man according to his works.

Matthew 6:6 - But thou, when thou prayest, enter into thy closet, and when thou hast shut thy door, pray to thy Father which is in secret; and thy Father which seeth in secret shall reward thee openly.

6) Spirit-filled lifestyle

Acts 4:31 - And when they had prayed, the place was shaken where they were assembled together; and they were all filled with the Holy Ghost, and they spake the word of God with boldness.

Galatians 5:16 - [This] I say then, Walk in the Spirit, and ye shall not fulfil the lust of the flesh.

7) Change your desires and affections

If we dilligently pray for God's will to be done in our lives, He will allign our desires with His plans for our life and grant what we ask for.

1 John 5:14-15 - And this is the confidence that we have in him, that, if we ask any thing according to his will, he heareth us:

Psalms 37:4 - Delight thyself also in the LORD; and he shall give thee the desires of thine heart.

Psalms 21:2 - Thou hast given him his heart's desire, and hast not withholden the request of his lips. Selah.

8) Lead you to your Purpose

Psalms 20:4 - Grant thee according to thine own heart, and fulfil all thy counsel.