Three measures of flour - Explanation 

Jesus Christ is not the Image of word alone, but the Image of invisible trinity God, that means in Jesus Christ we can see our Heavenly Father (I and the Father are one - John 10:30), and the Son (He who came down from heaven, that is, the Son of Man who is in heaven - John 3:13), and the Holy Spirit (if I do not go away, the Helper will not come to you - John 16:7).

Why Jesus Christ spoke about the parable of three measures of flour?

He told them another parable. The kingdom of heaven is like leaven that a woman took and hid in three measures of flour, till it was all leavened - Matthew 13:33

And again he said, To what shall I compare the kingdom of God? It is like leaven that a woman took and hid in three measures of flour, until it was all leavened - Luke 13:20-21