God's stories are testimonies of our personal experiences with our Living God at work in our lives; testifying how God heals and delivers us in difficult times and declaring His faithfulness, grace, mercies, goodness, love, care and many other attributes of Him. The very word testimony in Hebrew comes from a root word that means to repeat , to do again. The testimony is something to be repeated both in word and in deed. Therefore, when we declare the testimonies of God to people, we are setting them up to meet God in the same way we are declaring.
Joshua 4:6-7 (ESV)
6 ... When your children ask in time to come, ‘What do those stones mean to you?’ 7 then you shall tell them that the waters of the Jordan were cut off before the ark of the covenant of the Lord. When it passed over the Jordan, the waters of the Jordan were cut off.
Luke 8:38-39 (ESV)
38 ... Jesus sent him away, saying, 39 "Return to your home, and declare how much God has done for you." And he went away, proclaiming throughout the whole city how much Jesus had done for him."