“John 17:21-23 (KJV) 
21 That they all may be one; as thou, Father, art in me, and I in thee, that they also may be one in us: that the world may believe that thou hast sent me. 
22 And the glory which thou gavest me I have given them; that they may be one, even as we are one: 
23 I in them, and thou in me, that they may be made perfect in one; and that the world may know that thou hast sent me, and hast loved them, as thou hast loved me.”
Yesterday we looked at John 17 and one thing that stood out to us was the perfect unity of GOD and that Jesus Christ asked in His prayer for unity of His people (the church) five times. In the devotion “Unity of GOD’s people is a great witness – 2024.05.04 https://missioncommunities.network/2024/05/04/unity-of-gods-people-is-a-great-witness-2024-05-04/“ we touched on this. Let us look at it a bit more.
What does Jesus Christ mean with unity among His People?

I believe there are two aspects of unity:
The first one is when we are born again we become part of the body of Christ. 
“1 Corinthians 12:12-14 (KJV) For as the body is one, and hath many members, and all the members of that one body, being many, are one body: so also is Christ. 13 For by one Spirit are we all baptized into one body, whether we be Jews or Gentiles, whether we be bond or free; and have been all made to drink into one Spirit. 14 For the body is not one member, but many.”
We see when we are born again the Holy Spirit baptises us int the body of Christ, the church (this is different water and Holy Spirit baptism). Our spirit becomes part of His body the universal church. Every believer is part a part of His church. He also dwells in us by the Holy Spirit “Colossians 1:27 (KJV) To whom God would make known what is the riches of the glory of this mystery among the Gentiles; which is Christ in you, the hope of glory:” and in “1 John 4:13 (KJV) Hereby know we that we dwell in him, and he in us, because he hath given us of his Spirit.” Here we see one part of that unity that Jesus Christ prayed for. This is evident in our faith, that is in what we believe and therefore profess. “Ephesians 4:4-6 (KJV) There is one body, and one Spirit, even as ye are called in one hope of your calling; 5 One Lord, one faith, one baptism, 6 One God and Father of all, who is above all, and through all, and in you all.”. This aspect of unity, oneness, is a given an can not be altered (unless one defects from the faith).

The second aspect of this unity, I believe, is the outworking of that unity that it might be manifest, seen and expressed. This aspect of unity the enemy of our soul, the devil and His demons, will try to interfere with. Also the carnal nature, our physical body, as well as any un-sanctified part of our souls can bring disunity.
“1 Peter 5:8-9 (KJV) Be sober, be vigilant; because your adversary the devil, as a roaring lion, walketh about, seeking whom he may devour: 9 Whom resist stedfast in the faith, knowing that the same afflictions are accomplished in your brethren that are in the world.” and “John 10:10 (KJV) The thief cometh not, but for to steal, and to kill, and to destroy: I am come that they might have life, and that they might have it more abundantly.” One of the tactics of the devil is to sow disunity among the Church. This is what the LORD was addressing through Paul in 1 Corinthians 12:12:31. Here are some of the verse that follow on from verse 12 to 14 quoted before:
“1 Corinthians 12:15-27 (KJV) If the foot shall say, Because I am not the hand, I am not of the body; is it therefore not of the body? 16 And if the ear shall say, Because I am not the eye, I am not of the body; is it therefore not of the body? 17 If the whole body were an eye, where were the hearing? If the whole were hearing, where were the smelling? 18 But now hath God set the members every one of them in the body, as it hath pleased him. 19 And if they were all one member, where were the body? 20 But now are they many members, yet but one body. 21 And the eye cannot say unto the hand, I have no need of thee: nor again the head to the feet, I have no need of you. 22 Nay, much more those members of the body, which seem to be more feeble, are necessary: 23 And those members of the body, which we think to be less honourable, upon these we bestow more abundant honour; and our uncomely parts have more abundant comeliness. 24 For our comely parts have no need: but God hath tempered the body together, having given more abundant honour to that part which lacked: 25 That there should be no schism in the body; but that the members should have the same care one for another. 26 And whether one member suffer, all the members suffer with it; or one member be honoured, all the members rejoice with it. 27 Now ye are the body of Christ, and members in particular.”
We can see that disunity can occur and we also can see that in our experience in walking with Jesus Christ. This should not be the case as we seen in verse 25.
This part of unity, oneness, is dependant on us. GOD has provided the means to help us come to the outworked unity. “Ephesians 4:11-16 (KJV) And he gave some, apostles; and some, prophets; and some, evangelists; and some, pastors and teachers; 12 For the perfecting of the saints, for the work of the ministry, for the edifying of the body of Christ: 13 Till we all come in the unity of the faith, and of the knowledge of the Son of God, unto a perfect man, unto the measure of the stature of the fulness of Christ: 14 That we henceforth be no more children, tossed to and fro, and carried about with every wind of doctrine, by the sleight of men, and cunning craftiness, whereby they lie in wait to deceive; 15 But speaking the truth in love, may grow up into him in all things, which is the head, even Christ: 16 From whom the whole body fitly joined together and compacted by that which every joint supplieth, according to the effectual working in the measure of every part, maketh increase of the body unto the edifying of itself in love.”
When the ministries listed in verse 11 do their proper duty in then  the fruits will be what is listed in verses 13 to 16. As we, the saints, mature, that is growing more and more in the fruits of the Holy Spirit “Galatians 5:22-26 (KJV) But the fruit of the Spirit is love, joy, peace, longsuffering, gentleness, goodness, faith, 23 Meekness, temperance: against such there is no law. 24 And they that are Christ’s have crucified the flesh with the affections and lusts. 25 If we live in the Spirit, let us also walk in the Spirit. 26 Let us not be desirous of vain glory, provoking one another, envying one another.” We will more and more practice these fruits and therefore less and less “be desirous of vain glory, provoking one another, envying one another. (verse 26)” Therefore the expression of love for one another will foster that aspect of unity.
Therefore let us all endeavour to grow in maturity, and foster the expression of unity of our faith.
“Romans 12:18 (KJV) If it be possible, as much as lieth in you, live peaceably with all men.”
“Psalms 133:1-3 (KJV) A Song of degrees of David. Behold, how good and how pleasant it is for brethren to dwell together in unity! 2 It is like the precious ointment upon the head, that ran down upon the beard, even Aaron’s beard: that went down to the skirts of his garments; 3 As the dew of Hermon, and as the dew that descended upon the mountains of Zion: for there the LORD commanded the blessing, even life for evermore.”
Let us therefore dwell, that is live together, in unity, expressing GOD’s love by giving preferences to one another and let have love for each other as love cover a multitude of sins (1 Peter 4:8 ).

For further reading have a look 1 Corinthians 6:1-11 where verses 4 and 7 provides the solution to quarrels, especially verse 7 shows how love is outworked.