free Kindle volume, Chapel Library Resources offers a variety of quotations gleaned from his printed sermons. The book is divided into sections such as "salvation," "suffering," "the Bible," etc. The style of the book makes it easy to read in snatches and still find encouragement.
Some of my favorite quotes:
If you get condemnation out of the gospel, you put the condemnation into it yourselves! It is not the gospel, but your rejection of it that will condemn you.
Christ and His gospel will always be spoken against. If you know a gospel which is approved by the age and patronized by the learned, that gospel is a lie!
Faith is weakness clinging to strength.
These are days when we need men of principle, men who can put their foot down and keep it down, men who cannot be turned aside. They call this firmness, 'bigotry.' It is, however, only another name for Christian manliness!
There is a gladness among devils when we cease to pray!