The vineyard is the most well-known metaphor for God's people - both in the OT and NT. Jesus uses this metaphor in many of his parables: Mt 20:1-16; 21:28-31; 21:33-41; Mk 12:1-11; Luke 13:6-9; 20:9-16; John 15:1-8. In all these parables of the vineyard, there is this constant theme: fruitfulness is the expected outcome of the vineyard. God expects His vineyards (both OT & NT) to yield grapes in its season. When there is no grapes, the vineyard is destroyed or given to another.
In Isaiah's parable, the vineyard is "the house of Israel" and the garden are the "men of Judah." In other words, it is a reference to God's people in Isaiah's time. The Lord was looking for "good grapes" but it yielded only bad grapes. Instead of the good grapes of "justice" and "righteousness", He saw bad grapes of "bloodshed" and "cries of distress." God's people was busy with materialistic pursuits: buying and selling property, drinking and partying, compromising and confusing their moral and ethical values, accepting bribes, and generally ignoring God's word and law. As God's vineyard, Israel has failed to produce the fruits and therefore will be judged and its people will be removed from its land by the foreign invading hordes.
Has God's expectation changed under the New Covenant? Obviously not, because in one of Jesus' vineyard parables, he made it clear that God's judgment over Israel for rejecting the son (Christ) of the vineyard owner (God) is the loss of the Kingdom: "What then will the owner of the vineyard do to them? He will come and kill those tenants and give the vineyard to others" (Luke 20:15-16). The vineyard is a type of the Kingdom - the blessings and privileges of living under God's rule and reign. In John 15:1, Jesus speaks of himself as the Vine and God as the vineyard gardener. We who are members of His Kingdom are branches in this vineyard, whose main vine is Jesus Christ. Jesus makes it quite clear that even under the New Covenant, God the Father expects fruitfulness from His people: "He cuts off every branch in me that bears no fruit, while every branch that does bear fruit he prunes so that it will be even more fruitful. If anyone does not remain in me, he is like a branch that is thrown away and withers; such branches are picked up, thrown into the fire and burned. If you remain in me and my words remain in you, ask whatever you wish, and it will be given you. This is to my Father's glory, that you bear much fruit, showing yourselves to be my disciples. (John 15:2, 6-8).
Fruitfulness has two aspects: (1) the flesh - the "fruit" of the Spirit, viz., character aspect; (2) the seed - the multiplication aspect. We may say that fruitfulness is both being and doing. The focus in many discipleship training is on the first aspect - also called spiritual "formation". But the second aspect of spiritual "multiplication" is often ignored. In other word, it is discipleship without evangelism, flesh without seed.
Father help us to be fruitful and multiply, for this is the Great Commission given to us as disciples. Amen.