‘Peace be to this house!’”
εἰς ἣν δ’ ἂν εἰσέλθητε οἰκίαν, πρῶτον λέγετε Εἰρήνη τῷ οἴκῳ τούτῳ.
Luke said that Jesus told the 70 disciples that whatever house they entered (εἰς ἣν δ’ ἂν εἰσέλθητε οἰκίαν), they were first to say (πρῶτον λέγετε) “Peace be to this house (Εἰρήνη τῷ οἴκῳ τούτῳ)”. The early followers of Jesus were to bring peace not strife, but this was a standard greeting anyway. Matthew, 10:12 had Jesus give these same simple instructions to the 12 apostles. As they went into a house, they were to greet or pay respects to the people in the house. This was only common sense. You had to respect, greet, and bring peace to the people in whose house you entered. How do you greet people?
“As you enter
If the house
Let your peace
Come upon it.
But if it is not worthy,
Let your peace
Return to you!”
εἰσερχόμενοι δὲ εἰς τὴν οἰκίαν ἀσπάσασθε αὐτήν
καὶ ἐὰν μὲν ᾖ ἡ οἰκία ἀξία, ἐλθάτω ἡ εἰρήνη ὑμῶν ἐπ’ αὐτήν· ἐὰν δὲ μὴ ᾖ ἀξία, ἡ εἰρήνη ὑμῶν πρὸς ὑμᾶς ἐπιστραφήτω.
There are no exact equivalent passages in the other gospels about how to enter into a house. Jesus, via Matthew, had some simple instructions again. As you went into a house (εἰσερχόμενοι δὲ εἰς τὴν οἰκίαν), greet or pay respects to the people in the house (ἀσπάσασθε αὐτήν). If they were worthy people or the house was worthy (καὶ ἐὰν μὲν ᾖ ἡ οἰκία ἀξία), let your peace come upon them (ἐλθάτω ἡ εἰρήνη ὑμῶν ἐπ’ αὐτήν). But if they are not worthy or deserving (μὴ ᾖ ἀξία,), let your peace return or turn back to you (ἡ εἰρήνη ὑμῶν πρὸς ὑμᾶς ἐπιστραφήτω). I am not sure how you would get your peace greeting revoked in some way.