Philippians 2:18

For the same cause also do ye joy, and rejoice with me.

For the same cause that makes him rejoice, believers are called to share Paul's joy and to joy and rejoice together with him and with one another. This joint rejoicing belongs to doing all things without murmurings and disputings, so as to be blameless and harmless as sons of God without rebuke in the midst of a crooked and perverse nation, shining as lights in the world by holding forth the word of life, so that labor is not in vain. The joy remains even if he is offered upon the sacrifice and service of their faith, even if life itself is poured out upon it. His sacrifice does not cancel rejoicing but becomes part of its ground.

While toiling and laboring his satisfaction comes from knowing his efforts are bearing fruit as believers accept his labors and profit by them, and he asks them to joy and rejoice with him over that fruit. His being offered up and their faithful service to God are joint grounds for rejoicing together, and believers are to share joyfully with one another in that faithful service even when the service involves sacrifice. The rejoicing is expressed in praise to God, for praise glorifies Him, and thanksgiving spoken aloud strengthens and encourages those around them. In whatever calling or responsibility, every person is to do duty in faith, in obedience, in cheerfulness with hope and courage in the Lord, not seeking supremacy but leaving that with God and letting the work bring its own reward.

The verse calls the church to a thorough change of character before God can acknowledge them as His children. They are to have the mind that dwelt in Jesus in order to conduct themselves aright and to keep order in the church of God, and to observe the Sabbath correctly. That work brings forward testimonies and confessions of wrong, hearty repentance, and shame and confusion of face before God for an unrighteous course toward brethren and sisters.