Jesus Learned Obedience
But this is to misunderstand the word “through.” It is to read the word as if it means “by means of,” when in this context it surely means “in the midst of.” That is, Hebrews 5:8 does not mean “Jesus learned how to obey by means of his suffering,” but rather, “Jesus learned what obedience looked like in the midst of his suffering.” Here’s John Piper in The Passion of Jesus Christ:
... it doesn’t mean that he learned to stop disobeying. It means that with each new trial he learned in practice—and in pain—what it means to obey. When it says that he was “made perfect through suffering,” it doesn’t mean that he was gradually getting rid of defects. It means that he was gradually fulfilling the perfect righteousness that he had to have in order to save us ... If the Son of God had gone from incarnation to the cross without a life of temptation and pain to test his righteousness and his love, he would not be a suitable Savior for fallen man.