"Behold, how good and how pleasant it is for brothers to dwell together in unity!" Psalm 133:1

All who are Christ's are to live in unity. Let us see what Scripture will tells us of this unity (oneness, harmony, agreement). First of all, it is-- In Christ:
"So we, who are many, are one body in Christ and individually members one of another." Romans 12:5

"There is neither Jew nor Greek, there is neither slave nor free man, there is neither male nor female; for you are all one in Christ Jesus."
Galatians 3:28

"Therefore, if anyone is in Christ, he is a new creation; old things have passed away; behold, all things have become new." 2 Corinthians 5:17

The Apostle Paul speaking to the Ephesians in 4:4-6 gives an explanation of unity, "There is one body and one Spirit, just as you were called in one hope of your calling; one Lord, one faith, one baptism; one God and Father of all, who is above all, and through all, and in you all."
Paul then speaks of the gifts given to believers and in verses 12-16 tells of the purpose of the gifts, "Till we all come to the unity of the faith and the knowledge of the Son of God, to a perfect man, to the measure of the stature of the fullness of Christ." Vs. 13 (Read 4: 1-16)

Paul exhorts Believers to:
"Now I exhort you, brethren, by the name of our Lord Jesus Christ, that you all agree, and there be no divisions among you, but you be made complete in the same mind and in the same judgment." 1 Corinthians 1:10

"Finally, brethren, rejoice, be made complete, be comforted, be like-minded, live in peace; and the God of love and peace shall be with you."
2 Corinthians 13:11

"Being diligent to preserve the unity of the Spirit in the bond of peace."
Ephesians 4:3

"Only conduct yourselves in a manner worthy of the gospel of Christ; so that whether I come and see you or remain absent, I may hear of you that you are standing firm in one spirit, with one mind striving together for the faith of the gospel." Philippians 1:27

The Apostle Peter also give an exhortation to Believers:
"To sum up, let all be harmonious, sympathetic, brotherly, kindhearted, and humble in spirit." 1 Peter 3:8

David in Psalm 133 puts it this way,
"Behold, how good and how pleasant it is For brothers to dwell together in unity!
It is like the precious oil upon the head, Coming down upon the beard, Even Aaron's beard, Coming down upon the edge of his robes.
It is like the dew of Hermon,
Coming down upon the mountains of Zion;
For there the Lord commanded the blessing -- life forever."
(You can read of the anointing of Aaron in Exodus 29)

One in Christ! All gathered together in one flock. Jesus speaking to Pharisees in John 10:16 of those who will believe, "And I have other sheep, which are not of this fold; I must bring them also, and they shall hear My voice; and they shall become one flock with one shepherd."

Let us do as Paul tells us in Ephesians 4:3 and be "diligent to preserve the unity of the Spirit in the bond of peace."

Thank You Lord for our oneness in You and with each other. Amen