1 Corinthians 7:22
For he that is called in the Lord, being a servant, is the Lord’s freeman: likewise also he that is called, being free, is Christ’s servant. For he that is called in the Lord, being a servant, is the Lord’s freeman: likewise also he that is called, being free, is Christ’s servant.
The one who is called to faith in the Lord while a servant is the Lord's freed person, and the one who is called while free is Christ's servant. Social standing does not decide or alter a person's standing before God and belonging to Christ. All alike are servants of God and are to be willing to do His will. Those engaged in medical missionary work are therefore to minister to people of every social standing, high and low alike. Black believers belong to Christ just as truly as white believers do, and are not to be shut out from worship or from church membership.