After your identity in Christ is established and the miraculous life of the kingdom becomes more or less normal, at some point you'll be asked to show a stranger a miracle as evidence that you are the man (or woman) of God that you claim to be.
How do we respond to such a request?
Jesus worked miracles as part of the Father's witness to the message He carried. The miracles verified His message, not His identity. It's important to make a distinction between our message and our identity. They are not the same thing and they're not established in the same way.
When the religious leaders demanded that He give them a sign to prove by what authority he did things, they were bringing into question His identity. He replied that they would receive no sign from Him.
Why did he refuse to show them a sign?
When His identity was questioned, He could have worked a miracle to prove who he was. When He was questioned about His identity in the wilderness, Satan asked him to turn a rock into bread as proof of His identity. But Jesus refused. He knew who He was. He didn't need to establish His identity for anyone. He knew what the Father had said of Him at His baptism. That was all the proof He needed.
When our identity is called into question, the issues we're facing are insecurity and pride. If we're insecure in who we are in Christ or if we're proud of who we are, we'll give in to the temptation to prove our identity by working a miracle. In doing so, we fall into the enemy's trap.
After Jesus ascended into heaven, the Gospel of Mark says that the disciples "Went out and preached everywhere, the Lord working with them and confirming the word through the accompanying signs." (Mark 6:20)
The message we carry is to be confirmed with miracles, signs and wonders. But the miracles don't validate our identity. God establishes our identity and our identity is a matter that stays between God and us. It seems wise to avoid foolish conversations, disputes and challenges where people question our identity and demand proof of who we are by signs and miracles.
Once our true identity is established, we don’t need to be concerned with who we are, but rather who we represent. “We preach not ourselves, but Christ”. If we keep the focus on Him and not on us, the issue of our identity should never be a matter of discussion.