Mere Christianity Book IV Chapter 9 ("Counting the cost") : George MacDonald References In C.S. Lewis's book Mere Christianity, Book Four, Chapter 9 (&quot;Counting the cost&quot;) there are 2 illustrations that C.S. Lewis borrowed from George MacDonald.
The first:

And yet—this is the other and equally important side of it—
this Helper who will, in the long run, be satisfied with nothing
less than absolute perfection, will also be delighted with the
first feeble, stumbling effort you make tomorrow to do the
simplest duty. As a great Christian writer (George MacDonald)
pointed out, every father is pleased at the baby’s first attempt to
walk: no father would be satisfied with anything less than a
firm, free, manly walk in a grown-up son. In the same way, he
said, ‘God is easy to please, but hard to satisfy.’

The second:

I find I must borrow yet another parable from George
MacDonald. Imagine yourself as a living house. God comes in
to rebuild that house. At first, perhaps, you can understand
what He is doing. He is getting the drains right and stopping
the leaks in the roof and so on: you knew that those jobs
needed doing and so you are not surprised. But presently he
starts knocking the house about in a way that hurts abominably
and does not seem to make sense. What on earth is He
up to? The explanation is that He is building quite a different
house from the one you thought of—throwing out a new
wing here, putting on an extra floor there, running up towers,
making courtyards. You thought you were going to be made
into a decent little cottage: but He is building a palace. He
intends to come and live in it Himself.

The question: Which books / sermons / stories by George MacDonald do these references coming from?
The first one is from a sermon called The Father's Appeal, preached in Westminster Chapel:

“Though Jesus Christ is very hard to satisfy, He is very easy to please. Think of that and it will help you a little. He is very easy to please, but very hard to satisfy. If you will but let Him in, and you have not much to put on the table. You cannot share much of life because you have not got it, He will be so pleased, if it be but a cup of cold water that you can give him. Let it be something genuine, something real.”

I could not find the second one but MacDonald may have borrowed it from Book 1 Chapter 5 of The Confessions of St. Augustine:

My soul is like a house, small for you to enter, but I pray you to enlarge it. It is in ruins, but I ask you to remake it. It contains much that you will not be pleased to see: this I know and do not hide. But who is to rid me of these things? There is no one but you …