Shalom....allow me to interpret this saying for you beloved (knowing that all understanding comes directly from above). Leaven at times in the Word of G-d usually is referred to as evil (1 cor 5:6); But in this particular case, it is not. We must understand first the powerful dynamics of yeast itself or leaven; When yeast is kneaded in the dough, it expands by itself...the yeast in this parable is related to the Kingdom of G-d (the Spirit of G-d). We know from the Holy Scriptures that the Kingdom of G-d will grow from an internal dynamic; For the Lord Himself said, "...the kingdom of Heaven is within you". Now the woman can be directly related to Yeshua (Jesus) and the three measures of meal can absolutely be the Church and/or believers. Once the leaven has been applied or "hid" in the "meal" (believers), it is only then a matter of time until the Kingdom of G-d expands so mightily until the "whole" (the whole body of believers) becomes complete. As the parable of the mustard seed (matt 13:31,32) addresses the extent of the Kingdoms growth, this parable conerns with the power and 'process' of the growth....I hope this edifies you a little bit more my friend...Shalom!!