Today, the liturgical texts, through these two parables, place before our eyes one of the characteristics of the Kingdom of God: it is something that flourishes slowly —as a mustard seed— but, eventually, grows to offer shelter to the birds in its trees. Tertulian said it like this: «We come from yesterday and we fill everything». With this parable, Our Lord encourages us to patience, fortitude and hope. These virtues are especially necessary for those who devote themselves to propagate the Kingdom of God. We must be patient, and with God's grace and human cooperation, wait for the planted seed to grow while profoundly embedding its roots in the good soil to gradually become a tree. In the first place, we need to have faith in the virtuality —fecundity— contained in the seed of the Kingdom of God. This seed is the Word; it is also the Eucharist that is planted in us through Communion. Our Lord Jesus Christ compared himself to «a kernel of wheat that falls to the ground and dies (…). But if it dies, it produces many seeds» (Jn 12:24).
The Kingdom of God, our Lord goes on, is similar to «the yeast a woman has taken and hidden in three measures of flour until it is all leavened» (Lk 13:21). Here also the yeast capacity to leaven all the dough is mentioned. This is what happens with “the rest of Israel” which the Old Testament mentions: the rest will have to save and leaven all the people. Continuing on with the parable, we only need the yeast inside the dough, getting to the people, to be like salt that preserves from corruption and makes all food to taste (cf. Mt 5:13). Time is also of essence so that it can carry out with its function by and by.
Parables encouraging patience and the hopeful certainty; parables referring to the Kingdom of God and to the Church, and that are also applied to the growth of this same Kingdom in each of us.