I urge Euodia and I urge Syntyche to agree in the Lord.
Lord is the New Testament equivalent of YHWH. The one way to ensure that there is harmony within a somewhat contentious relationship within the church is to share a common focus on The One who is the center of our faith and The One who promotes true unity in the body. Lord Jesus cannot be divided. The Trinity is eternally in relationship and inextricably bound as one in essence, three in person. God the Father, God the Son and God the Holy Spirit – this is the true picture of perfect unity that has eternally existed. For true agreement in the body the Lord must be the focus. A relationship must be ‘in the Lord’. What does this look like?
I believe chapter 2 of Philippians describes it well. In addition, Paul uses the exact same word here when calling the ladies to ‘agree’ as he used in chapter 2 when he called the entire congregation to ‘be of the same mind’. This is only possible when the important things are central and emphasized and the petty things are endured by the grace of Christ Jesus.