What was Jesus reading? Isaiah 5

Jesus was reading from Isaiah 5:1-7,

¹ Let me sing for my beloved

       my love-song concerning his vineyard:

   My beloved had a vineyard

       on a very fertile hill.

²  He dug it and cleared it of stones,

       and planted it with choice vines;

   he built a watchtower in the midst of it,

       and hewed out a wine vat in it;

   he expected it to yield grapes,

       but it yielded wild grapes.

³  And now, inhabitants of Jerusalem

       and people of Judah,

   judge between me

       and my vineyard.

⁴  What more was there to do for my vineyard

       that I have not done in it?

   When I expected it to yield grapes,

       why did it yield wild grapes?

⁵  And now I will tell you

       what I will do to my vineyard.

   I will remove its hedge,

       and it shall be devoured;

   I will break down its wall,

       and it shall be trampled down.

⁶  I will make it a waste;

       it shall not be pruned or hoed,

       and it shall be overgrown with briers and thorns;

   I will also command the clouds

       that they rain no rain upon it.

⁷  For the vineyard of the LORD of hosts

       is the house of Israel,

   and the people of Judah

       are his pleasant planting;

   he expected justice,

       but saw bloodshed;

   righteousness,

       but heard a cry!   -Isaiah 5:1-7

when he formulated his parable about the vineyard in Matthew 21.

   ³³ "Listen to another parable. There was a landowner who planted a vineyard, put a fence around it, dug a wine press in it, and built a watchtower. Then he leased it to tenants and went to another country. ³⁴When the harvest time had come, he sent his slaves to the tenants to collect his produce. ³⁵But the tenants seized his slaves and beat one, killed another, and stoned another. ³⁶Again he sent other slaves, more than the first; and they treated them in the same way. ³⁷Finally he sent his son to them, saying, 'They will respect my son.' ³⁸But when the tenants saw the son, they said to themselves, 'This is the heir; come, let us kill him and get his inheritance.' ³⁹So they seized him, threw him out of the vineyard, and killed him. ⁴⁰Now when the owner of the vineyard comes, what will he do to those tenants?" ⁴¹They said to him, "He will put those wretches to a miserable death, and lease the vineyard to other tenants who will give him the produce at the harvest time."  -Matthew 21:33-41

It is very interesting to note that Jesus changes the sin in the vineyard from the prophesy in Isaiah to his parable. The sin in Isaiah is that the vineyard yielded wild grapes, whereas in the parable the tenants of the vineyard were preventing the owner from harvesting his grapes. This implies that the grapes were good grapes. Jesus is very importantly shifting the source of sin to the Jewish leadership. Their sin is that they are opposing God from harvesting what is rightfully his: the hearts of his people.