Ithamar (Hebrew אִֽיתָמָֽר, coast of the palm tree) (b. 2482 AM–fl. 1 Zif 2514 AM) (b. ca. 1523 BC–fl. 17 May 1490 BC) was the fourth son of Aaron and progenitor of a line of descent that briefly included some of the High Priests of Israel.
Ithamar's career began during the first year after the Exodus of Israel. He was treasurer of the massive voluntary offering of the people for the building of the Tabernacle. On 1 Zif 2514 AM (17 May 1490 BC) he was consecrated as a priest, together with his three brothers Nadab, Abihu, and Eleazar.
On the day of the strange-fire incident (10 Zif 2514 AM/26 May 1490 BC), all four brothers were performing a daily office in the Holy Place. Nadab and Abihu took censers charged with "strange fire" into the Holy of Holies, and were killed instantly. Moses ordered two other cousins to take the charred bodies away, and also ordered Aaron and his two remaining sons to continue with their duties and not show any outward sign of mourning. 
On that same occasion, Moses noticed that the meat for the sin offering had been burned entirely on the Brass Altar. The priests were supposed to eat from the sin offering in a clean place, but they had not done so. Moses interrogated Eleazar and Ithamar about this neglect of duty, and Aaron defended his sons. Apparently Aaron suggested that to eat any sort of meat when their brothers had recently died, and under such circumstances, might itself not seem pleasing to God. Moses reserved judgment. The Bible gives no indication that Eleazar or Ithamar made a similar mistake again.
Thereafter Eleazar and Ithamar were the two senior priests after Aaron. Ithamar, in addition, supervised the Gershonites and the Merarites who were responsible for dismantling and transporting the Tabernacle coverings, hangings, boards, bars, sockets, pillars, and other structural elements.
His line of descent (1_Chronicles 24:1-19 ) is most notable for the appearance of Judge Eli, his sons Hophni and Phinehas, his grandson Ichabod, and an apparently disloyal high priest named Abiathar whom Solomon removed from office during his reign and replaced with Zadok, an Eleazarite. That Eli and his son and grandson descend from Ithamar follows logically from the absence of their names in the line of descent from Eleazar given in 1_Chronicles 6:1-15 .
- Konig, George, "Ithamar," AboutBibleProphecy.com, 2001. Accessed December 10, 2008.
- "Ithamar," Easton's Bible Dictionary, July 13, 2005. Accessed December 10, 2008.
- Blank, Wayne, "The Lines of Eleazar and Ithamar," Daily Bible Study, n.d. Accessed December 10, 2008.
- Hirsch EG and Seligsohn M, "Ithamar," The Jewish Encyclopedia, n.d. Accessed December 10, 2008.
- Maxey A, "Eleazar and Ithamar," Reflections, no. 270, October 18, 2006. Accessed December 10, 2008.