The Greek ariston (ἄριστον) refers to the first or primary meal of the day — breakfast or the midday meal. It appears in Luke 11:37-38, where a Pharisee invites Jesus to dine (aristesei) and is surprised that He doesn't wash ceremonially before the meal; and in Luke 14:12 where Jesus instructs on who to invite to a banquet. Matthew 22:4 uses it for the wedding banquet feast.
Jesus at the Pharisee's ariston delivers one of His sharpest critiques of religious externalism: 'You Pharisees clean the outside of the cup and dish, but inside you are full of greed and wickedness' (Luke 11:39). The meal becomes a classroom. Jesus consistently used mealtimes as teaching moments — the feeding of 5,000, the Last Supper, the post-resurrection breakfast, the meal at Emmaus, and here. In Luke 14, the ariston becomes the occasion for the parable of the great banquet — those who were invited to the feast made excuses, so the host fills the table with the poor, lame, and blind. The kingdom's table is always more full than its original guest list.