Mark 16:15 says that believers are to go into all the world and preach the gospel to all creation… and these signs will accompany them… they will lay their hands on sick and they will be healed. So healing is a sign that Jesus is with us. Also, Jesus healed the sick when he was on earth, and Jesus is the exact image and representation of God. If we want to know what God was like in the bible, one way we can do that is by looking at Jesus. Because Jesus healed the sick, it was God’s will to heal the sick. If you want a more in depth theological response, try the link below. I personally disagree sightly with his conclusion but nevertheless its very thorough in its analysis.