It is of the greatest interest to look at the times in Luke’s gospel when Jesus said must.
Luke 2:49 “Why were you searching for me?” he asked. “Didn’t you know I must be in my Father’s house?”
Luke 4:43 But he said, “I must proclaim the good news of the kingdom of God to the other towns also, because that is why I was sent.”
Luke 9:22 And he said, “The Son of Man must suffer many things and be rejected by the elders, the chief priests and the teachers of the law, and he must be killed and on the third day be raised to life.”
Luke 13:33 “In any case, I must press on today and tomorrow and the next day—for surely no prophet can die outside Jerusalem!”