|Innermost chamber of Jesus' tomb|
The Resurrection, and the coming of the Holy Spirit, is what transformed the Apostles into men of boldness. The same Jesus Who had been raised to life after suffering death lived within them. They were not crippled by threats of financial hardship, physical suffering, or martyrdom because they knew that "He who raised Christ Jesus from the dead will give life to your mortal bodies also through his Spirit who dwells in you" (Rom.8:11).
Jesus' empty tomb is what allows us, today, to say, "If God is for us, then who cares who's against us?" (my paraphrase of Rom.8:31)