Suggested wording for a certificate:

Whereas Father God has adopted us into His Kingdom, and
Whereas the Lord Jesus has purchased us and men from every tribe and language and people and nation by His very precious blood shed on the cross (Rev. 5:9), and
Whereas the people of our culture have ready access to the Gospel and there are still Thousands of people in the world with no such access or Gospel witness, and
Whereas Christ has commended us and all Christians to preach the Gospel to the ends of the earth (Acts 1:8) and to make disciples of all nations (Mt 28:18-20)
We hereby adopt the
People Name
And pledge ourselves from this day forward to pray regularly for the establishment of a church among them and to continue to do so until our prayers are answered. In addition, we proclaim ourselves willing to be led by God into further involvement in the task of reaching the People Name, whether it be by sending workers to live among them, giving financially to the work among them, working to raise consciousness of their need within our church, or in any other way as God directs us. We pledge to diligently seek God's will for our church in regard to the People Name and to solemnly undertake to fulfill all the responsibilities inherent in the act of adoption as they are revealed to us by God.