What did Jesus mean when he said "Your words never return to you void..."

First of all, that quote is from the book of Isaiah. It's not Jesus, and it's not even from the New Testament. Secondly, it's Isaiah referring to the prophecy that he's putting forth. He's affirming the conviction he has in the words he's speaking.

Context!

Isaiah 55:8-11

1 “Come, all you who are thirsty,
come to the waters;
and you who have no money,
come, buy and eat!
Come, buy wine and milk
without money and without cost.
2 Why spend money on what is not bread,
and your labor on what does not satisfy?
Listen, listen to me, and eat what is good,
and your soul will delight in the richest of fare.
3 Give ear and come to me;
hear me, that your soul may live.
I will make an everlasting covenant with you,
my faithful love promised to David.
4 See, I have made him a witness to the peoples,
a leader and commander of the peoples.
5 Surely you will summon nations you know not,
and nations that do not know you will hasten to you,
because of the Lord your God,
the Holy One of Israel,
for he has endowed you with splendor.”
6 Seek the Lord while he may be found;
call on him while he is near.
7 Let the wicked forsake his way
and the evil man his thoughts.
Let him turn to the Lord, and he will have mercy on him,
and to our God, for he will freely pardon.
8 “For my thoughts are not your thoughts,
neither are your ways my ways,”
declares the Lord.
9 “As the heavens are higher than the earth,
so are my ways higher than your ways
and my thoughts than your thoughts.
10 As the rain and the snow
come down from heaven,
and do not return to it
without watering the earth
and making it bud and flourish,
so that it yields seed for the sower and bread for the eater,
11 so is my word that goes out from my mouth:
It will not return to me empty,
but will accomplish what I desire
and achieve the purpose for which I sent it.



"The proper idea: God’s word does what God wants it to. It prospers wherever he sends it. Not what we want; not where we send it. Whenever we misquote God, it’s no longer his word; it’s ours. We’ve taken it away from him, and abused it; we’ve made the sacred into something profane, a mockery of his original intent, like when the devil quotes it. And our words have no creative power without God behind them. They only have destructive power. They drive us and God apart, not close."

[link to morechrist.blogspot.ca]

WHO IS ISIAH!?