Prayer, in Old Testament times, was based upon a covenant relationship with God, or it was an appeal to His revealed nature as merciful, gracious, etc. Today it is based upon the redemptive work of Christ, whose death opened the way for us into the Father’s presence. This is why acceptable prayer today is offered “in the name of the Lord Jesus Christ”. With our Lord’s departure from this world in view, He said to His disciples:
“I am the way, the truth, and the life: no man cometh unto the Father but by Me” (John 14:6).
“Hitherto have ye asked nothing in My name…At that day ye shall ask in My name: and I say not unto you that I will pray the Father for you, for the Father Himself loveth you, because ye have loved Me…” (John 16:24-27).
Thus today we pray directly to the Father in the name of the Son.
Our prayers, however, are often faltering and sometimes the way is so dark before us that we do not even know what to ask for. Thus Paul declared: “We know not what we should pray for as we ought” (Rom. 8:26). But he was quick to follow this with the declaration:
“And we know that all things work together for good to them that love God, to them who are the called according to His purpose” (Rom. 8:28).
This is why the Apostle Paul encourages God’s people:
“Be careful [anxious] for nothing, but in everything, by prayer and supplication, with thanksgiving, let your requests be made known unto God:
“And the peace of God, which passeth all understanding, shall keep your hearts and minds through Christ Jesus” (Phil. 4:6,7).
“Let us therefore come boldly unto the throne of grace, that we may obtain mercy, and find grace to help in time of need” (Heb. 4:16). source