God's immutability and Prayer

I'm still working slowly through Stephan Charnock's book The Existence and Attributes of God. Here is an excerpt from one of the (long!) paragraphs speaking about God's unchangeableness being the ground and encouragement for our worship.

"When the highest promises are made, God expects they should be put in suit; our Saviour joins the promise and the petition together [Matt. 7:7]; the promise to encourage the petition, and the petition to enjoy the promise: he doth not say perhaps it shall be given, but it shall, that is, it certainly shall; your heavenly Father is unchangeably willing to give you those things. We must depend upon his immutability for the thing, and submit to his wisdom for the time. Prayer is an acknowledgment of our dependence upon God; which dependence could have no firm foundation without unchangeableness. Prayer doth not desire any change in God, but is offered to God that he would confer those things which he hath immutably willed to communicate; but he willed them not without prayer as the means of bestowing them. The light of the sun is ordered for our comfort, for the discovery of visible things, for the ripening the fruits of the earth; but withal it is required that we use our faculty of seeing, that we employ our industry in sowing and planting, and expose our fruits to the view of the sun, that they may receive the influence of it. If a man shuts his eyes, and complains that the sun is changed into darkness, it would be ridiculous; the sun is not changed, but we alter ourselves; nor is God changed in not giving us the blessings he hath promised, because he hath promised in the way of a due address to him, and opening our souls to receive his influence, and to this, his immutability is the greatest encouragement." (emphasis added)

I realize the wording is a bit convoluted, but just take some time to chew on things a bit and you will be blessed. Have a great day, basking in the encouragement and comfort of God's unchangeableness!