The doors were locked by Jerome

“ Do you want to know how he was born of a Virgin and how, after his birth, his Mother remained a virgin? The doors were locked, yet Jesus entered. There is no doubt that the doors were locked. He who entered through the locked doors was not a phantasm or a ghost but a true body. For what did he say? “Look at me and see that a ghost does not have flesh and bones as I do” (Lk 24:30).”

Jerome, “Homilia in Joannem 1, 1-14; CCL 78, 521.