2 Chronicles 32:30 Commentary - English Annotations on the Holy Bible by Matthew Poole
The upper water-course of Gihon; a rivulet near Jerusalem consisting of two streams, the upper, which was brought into one pool, called the upper pool, Isa 7:3; and the lower, which was brought into another, called the lower pool, Isa 22:9. The former he diverted and brought by secret pipes into Jerusalem, which was a work of great art, and labour, and policy, and therefore is here commended.
Brought it straight down; whereas before it fetched a compass, and thereby might have been beneficial to the Assyrian host.
Consult other comments:
2 Chronicles 32:30 - Albert Barnes' Notes on the Bible
2 Chronicles 32:30 - Joseph Benson’s Commentary on the Old and New Testaments
2 Chronicles 32:30 - The Cambridge Bible for Schools and Colleges
2 Chronicles 32:30 - Adam Clarke's Commentary and Critical Notes on the Bible
2 Chronicles 32:30 - Companion Bible Notes, Appendices and Graphics
2 Chronicles 32:30 - Ellicott's Commentary for English Readers (Old and New Testaments)
2 Chronicles 32:30 - Geneva Bible Notes
2 Chronicles 32:30 - John Gill's Exposition of the Entire Bible
2 Chronicles 32:30 - English Annotations on the Holy Bible by Matthew Poole
2 Chronicles 32:30 - John Trapp's Complete Commentary (Old and New Testaments)
English Annotations on the Holy Bible by Matthew Poole

Matthew Poole (1624–1679) wrote English Annotations on the Holy Bible, completing the chapters as far as Isaiah 58 before his death in 1679. The rest of the Annotations were completed by friends and colleagues among his Nonconformist brethren. The first printing of the completed edition was in 1685, 2 volumes folio, followed by editions in 1688, 1696 (with valuable chapter outlines added by the editors, Samuel Clark and Edward Veale), and the 4th and definitive edition in 1700, the basis of all others.