"For He says to Moses, “I will have mercy on whom I have mercy, and I will have compassion on whom I have compassion.” So then it does not depend on the man who wills or the man who runs, but on God who has mercy." - Rom 9:15-16
The Reformed Faith: An Exposition Of The Westminster Confession Of Faith (eBook)
by Robert Shaw. This is considered by many (along with A. A. Hodge's Commentary) to be the best commentary on the Westminster Confession.
The Glorious Feast of the Gospel (eBook)
by Richard Sibbes - Delivered in diverse sermons upon Isaiah 25:6-9.