Bible dictionaries
Ithra
What Bible dictionaries say about “Ithra”, one article after the other.
International Standard Bible Encyclopedia (ISBE 1915)
ith'-ra (yithra', "abundance"): The father of Amasa, commanding general in the rebel army of Absalom. It seems that his mother was Abigail, a sister or half-sister of King David (1Ch 2:17). She is called the sister of Zeruiah, Joab's mother (2Sa 17:25). In this same passage Ithra is called an "Israelite," but in 1Ch 2:17; 1Ki 2:5,32, we read: "Jether the Ishmaelite."
International Standard Bible Encyclopedia — James Orr, general editor and contributors; CrossWire SWORD module ISBE 2.2
The article in ISBE 1915Smith’s Bible Dictionary
(excellence), an Israelite, (2 Samuel 17:25) or Ishmaelite, (1 Chronicles 2:17) the father of Amasa by Abigail, Davids sister. (B.C. before 1023.)
William Smith; revised by F. N. Peloubet and M. A. Peloubet; CrossWire SWORD module Smith 1.3
The article in Smith