Albert Barnes on Luke 13:25

When once the master, &c. The figure here used is taken from the conduct of a housekeeper, who is willing to see his friends, and who at the proper time keeps his doors open. But there is a proper time for closing them, when he will not see his guests. At night it would be improper and vain to seek an entrance--the house would be shut. So there is a proper time to seek an entrance into heaven; but there will be a time when it will be too late. At death the time will have passed by, and God will be no longer gracious to the sinner's soul.

(w) "When once the master" Ps 32:6, Is 55:6 (x) "hath shut the door" Mt 25:10 (y) "Lord, Lord open to us" Lk 6:46