Using the words "in the Name of Jesus" or better, more respectfully, "in the name of the Lord Jesus Christ" and similar, at the end of prayers, has been the custom for time immemorial. To many people they are just the final words of any prayer, followed automatically by the Amen. It would seem that the prayer is not quite finished without these words.
As a rule the expression "in the name of …" or "on behalf of …" is used to indicate one person representing another under his authority. For example, an assistant or secretary will sign a letter dictated or drafted by his boss after the word "for", which indicates that although he is signing, it is under the authority of his boss, whose name is given immediately after. The boss assumes full responsibility though the signature is not his own, so long as the person signing really has his authority and with the words "on behalf of", "for" or similar indicates that he signs in his name.
The Lord Jesus told His disciples "…I go to My Father, and whatever you ask in My name, that I will do, that the Father may be glorified in the Son. If you ask anything in My name, I will do it." John 14:13-14 (NKJV)." Let us observe carefully the clarity with which He determines to Whom the request ought to be made (the Father), Who is going to comply with the request (the Son), who makes the request (the disciples), in Whose name (the Son) and the purpose (that the Father may be glorified in the Son). According to the above rule, the Lord Jesus was teaching that He would comply with all that was requested by the disciples from the Father with His own authority and under His own responsibility.
Not only the disciples to whom the Lord Jesus was speaking obtained His authority to pray in His Name. The apostle Paul explained to the believers of the church in Corinth: "… you were washed, you were sanctified, you were justified in the name of the Lord Jesus and by the Spirit of our God." 1 Corinthians 6:11 (NKJV). And, to the Colossian Christians: "whatever you do in word or deed, do all in the name of the Lord Jesus, giving thanks to God the Father through Him." Col. 3:17 (NKJV). Like the members of the church in Corinth, everyone who has been washed, sanctified and justified in the name of the Lord Jesus and by the Holy Spirit is under obligation to only speak and act with the authority and under the responsibility of the Lord Jesus, giving thanks to God the Father for Him. This includes prayers to God the Father.
This is the high standard for the life of every believer, as the apostle Paul wrote to the believers in Galatia "I have been crucified with Christ; it is no longer I who live, but Christ lives in me; and the life which I now live in the flesh I live by faith in the Son of God, who loved me and gave Himself for me." Gal. 2:20 (NKJV). The believer's golden rule is to always have in mind the question: "Would the Lord Jesus do - or say - this?" before any action or word, for we are acting in His name.
However, even after we have been saved through our faith in Christ, and are sealed with the Spirit of God, we still have our old nature in us, which fights against the new one we received from God. "'The Lord knows those who are His,' and, 'Let everyone who names the name of Christ depart from iniquity.'" 2 Timothy 2:19 (NKJV).
If we use the name of Christ before the world, let us ensure that sin is swept from our lives. Regrettably there are those who assert that they faithfully observe the good apostolic doctrine, but they do not bear with or show any love, patience, or long-suffering for their brethren in Christ, or are caught in other equally serious sins. The Lord knows the heart and knows those who are His, but the world only sees the outside.
There would be no need for the exhortation for us to depart from iniquity if automatically all our actions and words came from the Lord Jesus. We must therefore admit that, unfortunately, we are not always behaving or speaking with the authority and under the responsibility of Christ. Even when we pray.
To formally say "in the name of the Lord Jesus Christ" does not authenticate any prayer. It is necessary that whoever prays, and what he prays for, are authorized by Him: authority has only been given to His disciples and to those who have received Him as their Lord and Saviour, and He only takes responsibility for the requests made by them according to His will.
To pray in the name of the Lord Jesus Christ means to stand in His place, identified with Him, in fellowship with Him. No sinner can come before God in his own name, and He will only hear the prayers which are made by His Son, through His servants: those who received Him as Lord of their lives. God will hear the prayer which allows Him to be glorified in His Son.
Therefore, when we pray in the name of the Lord Jesus, we shall not be praying for something which we selfishly want for ourselves, but for Him, for His work, for that which we know is His will. We shall also be living in obedience to the Lord Jesus, for the promise of answer is made to those who love Him, and the evidence that we love Him is in obeying His commandments, of which the first is to love one another.
Finally, therefore, is it a redundancy to end a prayer with the words "in the name of the Lord Jesus"? Even assuming that we are His obedient servants, and that what we are asking for conforms with His will, it is never too much, or redundant, for us to clearly declare, so that all may hear, that we are not asking in our own name, which would be unacceptable, but only through the merits and in the name of our Lord and Saviour.
It is true that God knows our hearts, and knows if this is so, but by pronouncing these words we are saying that we obey His command, and remember it. In this manner we also announce it to all who are hearing us, so that the Father may be glorified in the Son, according to His wishes. How can this be done if He is not even mentioned?
But beware of dissimulation! The use of these words by who is not authorised or who is asking for something which is not in conformity with the will of the Lord Jesus Christ will not make his request acceptable.