en_tn/mat/24/43.md

that if the master of the house ... broken into

Jesus uses a parable of a master and servants to illustrate that his disciples should be prepared for his return. (See: rc://en/ta/man/translate/figs-parables)

the thief

Jesus is saying he will come when people are not expecting him, not that he will come to steal. (See: rc://en/ta/man/translate/figs-metaphor)

he would have been on guard

"he would have guarded his house"

would not have allowed his house to be broken into

This can be stated in active form. Alternate translation: "would not have allowed anyone to get into his house to steal things" (See: rc://en/ta/man/translate/figs-activepassive)