Talmud do Rodzaju 3:9

A person should never enter into someone else's house suddenly.³Cf. Nid. 16b (Sonc. ed., p. 112). And all people should learn derekh eretz (proper behavior) from the Omnipresent, Who stood at the entrance to the Garden [of Eden] and called to Adam,⁴To announce His presence. as it is stated, "And God called to Adam and said, 'Where are you?'"⁵Gen. 3:9.
The story is told of the four Sages, viz. Rabban Gamaliel, R. Joshua, R. Eleazar b. Azariah and R. ‘Aḳiba, who were on their way to attend a Privy Council⁶Or, lit. ‘an interior kingdom’. which also included a certain philosopher as a member. R. Joshua said to Rabban Gamaliel, ‘Master, would you like us to call on our companion the philosopher?’⁷To confer with him before the meeting. He replied, ‘No’. In the morning he again asked him, ‘Master, would you like us to call on our companion the philosopher?’ He replied, ‘Yes’. R. Joshua went and knocked on the door. The philosopher thought and said [to himself], ‘This can only be the manners of a Sage’. [When he knocked] a second time, [the philosopher] got up and washed his face, hands and feet. On the third knock he arose and opened the door and saw the Sages of Israel coming all together.⁸lit. ‘some from here and some from there’. Rabban Gamaliel was in the middle, R. Joshua and R. Eleazar b. Azariah on his right and R. ‘Aḳiba on his left.
The philosopher was meditating and saying [to himself], ‘How shall I greet these Sages of Israel? If I say, “Peace be upon you, Rabban Gamaliel”, I shall be guilty of derogatory conduct towards the [other] Sages. If I say, “Peace be upon you, Sages of Israel”, that would be an insult to Rabban Gamaliel’.⁹Who had the title of Prince or Patriarch, and was President of the Great Sanhedrin in Jerusalem. As soon as he approached them, he greeted them with the words, ‘Peace be upon you, Sages of Israel, headed by Rabban Gamaliel’.
(We learn [this rule of etiquette] not from [this story of] Rabban Gamaliel but from the Divine Presence, as it is stated, I saw the Lord sitting on His throne, and all the host of heaven standing by Him on His right hand and on His left.)¹⁰1 Kings 22, 19. This passage is omitted by GRA and printed in V within brackets. He inserts it in chap. IV towards the end and reads: ‘We learn this [rule] not only from the angels but from the Divine Presence’, etc.

¹This Baraitha is derived mainly from DER VI.BARAITHA. One should not take leave of his teacher or his friend without receiving permission. This rule of good manners all men may learn from the All-present, Who stood at the entrance of the Garden [of Eden] and called to Adam, as it is stated, And the Lord God called unto the man [’Adam], and said unto him: Where art thou?²Gen. 3, 9. God was about to part from Adam (cf. ibid. 24).
One should not be impatient during his meal. It is reported of Hillel that once a man came to have a meal with him, when a poor person arrived and, standing at the door of his house, said to his wife, ‘I am to be married today and I have no food’. She took the entire meal and gave it to him. Then she went and kneaded fresh dough, cooked another meal and came in and placed it before them. [Hillel] said to her, ‘My dear, why did you not bring this sooner?’ She told him what had happened; whereupon he said, ‘My dear, I did not judge you in the scale of guilt but in the scale of merit, because all your deeds are for the sake of Heaven’.