John Gill Commentary 2 Chronicles 24:1

"Joash was seven years old when he began to reign; and he reigned forty years in Jerusalem: and his mother`s name was Zibiah, of Beer-sheba." — 2 Chronicles 24:1 (ASV)

Ver. 1,2. Joash was seven years old when he began to reign
2 Chronicles 24:2

(See Gill on 2 Chronicles 24:1).