“And at the season he sent to the husbandmen a servant, that they should give him of the fruit of the vineyard, but the husbandmen beat him, and sent him away empty. And he sent yet another servant, and him also they beat, and handled him shamefully, and sent him away empty. And he sent yet a third, and him also they wounded, and cast him out.”
When the appropriate time came, and no fruit was forthcoming, the owner then sent a number of servants, one by one, in order to collect His portion of the fruit of the vineyard. But in each case the servants were handled shamefully in order to discourage them from persisting or returning. As so often ‘three' indicates completeness. These three cover all the prophets and men of God down to John.
None would have any difficulty here in recognising that this indicated all godly men who had sought to speak to Israel, and none more so than the true prophets whose treatment by Israel/Judah was a byword.
‘Sent -- a servant.' See Jeremiah 7:25-26 - ‘I have sent unto you all my servants the prophets, day by day rising up early and sending them -- but they made their neck stiff and did worse than their fathers', and 2 Chronicles 24:19 - ‘yet He sent prophets to them to bring them again to the Lord'. (See also Matthew 23:30-36). Compare also 2 Chronicles 36:15-19, ‘the Lord, the God of their fathers, sent persistently to them by His messengers, because He had compassion on His people, and on His dwellingplace, but they kept mocking the messengers of God, despising His words and scoffing at His prophets, until the wrath of the Lord arose against His people, until there was no remedy --- therefore He slew their young men with the sword in the house of their sanctuary ---and they burned down the house of God and broke down the walls of Jerusalem'. None knew better than Jesus that history repeats itself. For the maltreatment of successive men of God see also 1 Kings 18:13; 1 Kings 22:27; 2 Chronicles 24:20-21; Nehemiah 9:26; and for the sending of prophets, Jeremiah 25:4; Amos 3:7 Zechariah 1:6. The consequences that followed are also clearly described.
Note that Luke deliberately leaves out the mention of the death of some of the servants. He wants to emphasise the contrast between the servant and the son. It is only the Son Whose death is really significant.