To capture the context of the Great Supper parable, it's best to read what was going on when Jesus told it. Jesus was going to eat supper with a man and his friends –all self-righteous men at that! That sets the theme of the whole story; it's a contrast between self-righteousness and humility.
One Sabbath, when Jesus went to eat in the house of a prominent Pharisee, he was being carefully watched. There in front of him was a man suffering from dropsy. Jesus asked the Pharisees and experts in the law, "Is it lawful to heal on the Sabbath or not?" But they remained silent. So taking hold of the man, he healed him and sent him away. Then he asked them, "If one of you has a son or an ox that falls into a well on the Sabbath day, will you not immediately pull him out?" And they had nothing to say.
When he noticed how the guests picked the places of honor at the table, he told them this parable: "When someone invites you to a wedding feast, do not take the place of honor, for a person more distinguished than you may have been invited. If so, the host who invited both of you will come and say to you, 'Give this man your seat.' Then, humiliated, you will have to take the least important place. But when you are invited, take the lowest place, so that when your host comes, he will say to you, 'Friend, move up to a better place.' Then you will be honored in the presence of all your fellow guests. For everyone who exalts himself will be humbled, and he who humbles himself will be exalted."
Then Jesus said to his host, "When you give a luncheon or dinner, do not invite your friends, your brothers or relatives, or your rich neighbors; if you do, they may invite you back and so you will be repaid. But when you give a banquet, invite the poor, the crippled, the lame, the blind, and you will be blessed. Although they cannot repay you, you will be repaid at the resurrection of the righteous." (Luke 14:1-14)
Providing for the outcasts –and especially without the recognition– is outlandish to those who are outwardly religious. Now let's see how that sets up the backdrop for the parable.
When one of those at the table with him heard this, he said to Jesus, "Blessed is the man who will eat at the feast in the kingdom of God."
Jesus replied: "A certain man was preparing a great banquet and invited many guests. At the time of the banquet he sent his servant to tell those who had been invited, 'Come, for everything is now ready.' But they all alike began to make excuses. The first said, 'I have just bought a field, and I must go and see it. Please excuse me.' Another said, 'I have just bought five yoke of oxen, and I'm on my way to try them out. Please excuse me.' Still another said, 'I just got married, so I can't come.'"
"The servant came back and reported this to his master. Then the owner of the house became angry and ordered his servant, 'Go out quickly into the streets and alleys of the town and bring in the poor, the crippled, the blind and the lame.'
"'Sir,' the servant said, 'what you ordered has been done, but there is still room.'
"Then the master told his servant, 'Go out to the roads and country lanes and make them come in, so that my house will be full. I tell you, not one of those men who were invited will get a taste of my banquet.'" (Luke 14:15-24)
Yes, the man having the feast represents our Heavenly Father; and the Great Supper (or Great Feast) is the "marriage supper of the Lamb". But who are represented by the two groups of people; and what is really meant?
First there are those who are preoccupied with themselves; Jesus is referring to His Jewish brothers –particularly the religious men– who had been turning away from God since the nation was first formed. They considered themselves to be "healthy" and have no need for changing their condition. The poor, the crippled, the blind and the lame all know that they are "sickly". For both, Jesus was referring to their need for spiritual healing –their need a savior.
On hearing this, Jesus said, "It is not the healthy who need a doctor , but the sick. But go and learn what this means: 'I desire mercy, not sacrifice.' For I have not come to call the righteous, but sinners. (Matthew 9:12-13)
Jesus' parables, by their very nature, contain hidden meanings that are only revealed to the humble hearted. (See Parables.) So when He told them to "learn what this means" Jesus knew that they would have to first seek God. And that meant they would then find their savior.
What puzzles so many is that God makes the first group –the prideful, defiant, stubborn people– come in too. Obviously, He isn't forcing them to be saved, so what's going on here? Notice that He didn't make them sit at the table as guests of the Bridegroom. Rather, He had them come in to see and acknowledge what was happening –to see what they missed. It's a time when all will confess that Jesus is Lord!