“Jesus Christ yesterday and today is the same and to the ages” https://biblehub.com/text/hebrews/13-8.htm This is what the closest disciples and apostles believed just decades after Jesus Christ was born. How can you believe that except you believe there is preexistence? Did they believe it because they watched Jesus growing up and noticed He never changed? No. Obviously not. It is there in the nature of Jesus which they saw over just a few years following Him and especially after the resurrection when He was still the same Jesus. They matched what they saw with what He said about Himself. “I am”. They knew it meant He is existent over time in a mysterious yet real way and more so than other people. This gave them faith it would continue “into the ages” ahead. That is the essential belief Jesus spoke of in John 8. That is part of Jesus being the Christ, the Son of Man.
