One example of a New Testament promise attached to a command is found in Matthew 6:33. Jesus commands his followers to seek first the kingdom of God and his righteousness, and he promises that God will then provide for all their needs. Another example can be found in John 15:7, where Jesus commands his disciples to remain in him, and he promises that if they do, they can ask for whatever they wish and it will be done for them. These promises demonstrate the connection between obedience to God's commands and the fulfillment of those promises.
