I have J.A. Pipa Jr.'s study guide of the WCF. I haven't gone through it yet, but it looks pretty good. Not really a commentary though...

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Brian Vandenburg
Member of Westminster Presbyterian Church (PCA)
Vancouver, WA
"The authority of the Holy Scripture, for which it ought to be believed, and obeyed, depends not upon the testimony of any man, or Church; but wholly upon God (who is truth itself) the author thereof: and therefore it is to be received, because it is the Word of God."-Westminster Confession of Faith