And whatsoever ye do in word or deed, do all in the name of the Lord Jesus, giving thanks to God and the Father by him. (Colossians 3:17)
During Jesus' conversation with the 11 remaining disciples, He let them know that all that they did in the way of ministry was to be done in His name:
And these signs shall follow them that believe; In my name shall they cast out devils; they shall speak with new tongues; Mark 16:17
What a powerful promise! Whatever we ask In His Name, we will receive!
Peter, after his conversion, understood the magnitude of the birth, life, death and resurrection of Jesus.
Neither is there salvation in any other: for there is none other name under heaven given among men, whereby we must be saved. (Acts 4:12)
Before Jesus' crucifixion, He taught the disciples the importance of praying in the proper way:
Hitherto have ye asked nothing IN MY NAME; ask, and ye shall receive, that your joy may be full. (John 16:24)
"Hitherto" means "up until now." Up until the time Jesus spoke these words, His followers had asked nothing in His name. At this point He established a new relation with them. He told them to ask God for things in His name:
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. (John 16:23)
Don’t get this great promise confused. This promise has to be taken along with the other principles of prayer taught in the Bible. We can never isolate one verse on a subject without considering all that is taught on that subject in the Word of God. For example, the Bible teaches you cannot ask selfishly:
Ye ask, and receive not, because ye ask amiss, that ye may consume it upon your lusts. (James 4:3)
Confess your faults one to another, and pray one for another, that ye may be healed.
The effectual fervent prayer of a RIGHTEOUS man avails much. (James 5:16)
If ye abide in Me, and My words abide in you, ye shall ask what ye will, and it shall be done unto you. (John 15:7)
This means IF we are abiding in Christ we can ask and it shall be done. IF we are walking in obedience to God's Word, then we can ask in the name of Jesus.
Father, if thou be willing, remove this cup from me: nevertheless not my will, but thine be done. (Luke 22:42)
Likewise the Spirit also helps our infirmities: FOR WE KNOW NOT WHAT WE SHOULD PRAY FOR AS WE OUGHT; but the Spirit itself makes intercession for us with groanings which cannot be uttered. And He that searches the hearts knows what is the mind of the Spirit, because He makes intercession for the saints according to the will of God. (Romans 8:26-27)
And He gave them their request; but sent leanness into their soul. (Psalms 106:15)
Giving thanks always for all things unto God and the Father IN THE NAME of our Lord Jesus Christ. (Ephesians 5:20)
By Him therefore let us offer the sacrifice of praise to God continually, that is, the fruit of our lips giving thanks TO HIS NAME. (Hebrews 13:15)