Jesus compared the kingdom of heaven to a tiny mustard seed that grows large and to leaven that works through the whole measure of flour. He taught the crowds in parables, fulfilling what had been spoken through the prophet (Matthew 13:31-35).
31He put before them another parable: “The kingdom of heaven is like a mustard seed that a man planted in his field. 32Although it is the smallest of all seeds, yet it grows into the largest of garden plants and becomes a tree, so that the birds of the air come and nest in its branches.” 33He told them still another parable: “The kingdom of heaven is like leaven that a woman took and mixed into three measures of flour, until all of it was leavened.”
Matthew says that Jesus' teaching of the crowds in parables fulfilled the psalmist's words about opening his mouth in parables and uttering hidden things.
I will open my mouth in parables; I will utter things hidden from the beginning,
Psalm 78:2 speaks of opening the mouth in parables and uttering hidden things; Matthew 13:34-35 says that Jesus taught the crowds in parables and quotes those words as fulfilled.