Answer: We should imitate the faith of the leaders, who spoke the Word of God to us, considering the outcome of their way of life, (verse 7).
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Though this is good advice for Christians concerning the leaders of their congregations, this verse is probably speaking of past leaders, who are now dead, or of the apostles, whose teachings were inspired by the Holy Spirit and are now the Word of God in written New Testament form. On the other hand, verse 17 of this chapter is speaking of current leaders--"Obey your leaders and submit to their authority," as is verse 24. Examples of this would be:
1 Corinthians 4:14-17: [Paul says,] "I am not writing this to shame you, but to warn you, as my dear children. Even though you have ten thousand guardians in Christ, you do not have many fathers, for in Christ Jesus I became your father through the Gospel. Therefore I urge you to imitate me. For this reason I am sending to you Timothy, my son whom I love, who is faithful in the Lord. He will remind you of my way of life in Christ Jesus, which agrees with what I teach everywhere in every church."
Ephesians 5:1-2: "Be imitators of God, therefore, as dearly loved children and live a life of love, just as Christ loved us and gave Himself up for us as a fragrant offering and sacrifice to God."
1 Thessalonians 1:6-7: "You became imitators of us and of the Lord; in spite of severe suffering, you welcomed the message with the joy given by the Holy Spirit. And so you became a model to all the believers in Macedonia and Achaia."
1 Thessalonians 2:14a: "For you, brothers, became imitators of God's churches in Judea, which are in Christ Jesus..."
Hebrews 6:12: "We do not want you to become lazy, but to imitate those who through faith and patience inherit what has been promised."
3 John 11: "Dear friend, do not imitate what is evil but what is good. Anyone who does what is good is from God. Anyone who does what is evil has not seen God."