Which Scripture supports the doctrine of the Trinity by stating, "Baptize them in the name of...?"

The correct choice is supported by Matthew 28:19, which contains the directive, "Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit." This verse is significant for the doctrine of the Trinity as it explicitly mentions each person of the Godhead: the Father, the Son, and the Holy Spirit. The way this commission is phrased indicates a unity in authority and essence among the three, affirming the core belief in one God existing in three distinct persons.

In contrast, the other options do not explicitly articulate the Trinitarian formula. 1 Peter 1 discusses the role of the Father, the Spirit, and Jesus Christ but does not present the baptismal command associated with the Trinity. John 17 includes Jesus' prayer for unity among believers but does not dwell on the doctrine of the Trinity directly. Hebrews 5 focuses on Jesus as the high priest and does not directly address the concept of the Trinity or baptism. Thus, Matthew 28 is a foundational scripture for understanding and supporting the doctrine of the Trinity in the context of Christian baptism.