Matthew 18:19
"Again I say unto you, That if two of you shall agree on earth as touching any thing that they shall ask, it shall be done for them of my Father which is in heaven."
Cross References (ranked by relevance)
Ask, and it shall be given you; seek, and ye shall find; knock, and it shall be opened unto you:
Therefore I say unto you, What things soever ye desire, when ye pray, believe that ye receive them, and ye shall have them.
For I know that this shall turn to my salvation through your prayer, and the supply of the Spirit of Jesus Christ,
And in that day ye shall ask me nothing. Verily, verily, I say unto you, Whatsoever ye shall ask the Father in my name, he will give it you.
And all things, whatsoever ye shall ask in prayer, believing, ye shall receive.
If ye abide in me, and my words abide in you, ye shall ask what ye will, and it shall be done unto you.
Ye have not chosen me, but I have chosen you, and ordained you, that ye should go and bring forth fruit, and that your fruit should remain: that whatsoever ye shall ask of the Father in my name, he may give it you.
Peter therefore was kept in prison: but prayer was made without ceasing of the church unto God for him.
These all continued with one accord in prayer and supplication, with the women, and Mary the mother of Jesus, and with his brethren.
But we will give ourselves continually to prayer, and to the ministry of the word.
Leave there thy gift before the altar, and go thy way; first be reconciled to thy brother, and then come and offer thy gift.