The hymn of praise sung by Jesus and the eleven disciples after the Lord's Supper (Mark 14: 26), as was customary at the end of a Passover meal. It was part of Psalms 115–18, which were praises inspired by the story of the Exodus.
Citation for hallel
Citation styles are based on the Chicago Manual of Style, 15th Ed., and the MLA Style Manual, 2nd Ed..
MLA
"hallel." In A Dictionary of the Bible. Ed. W. R. F. Browning. Oxford Biblical Studies Online. May 19, 2013. <http://www.oxfordbiblicalcstudies.com/article/opr/t94/e815>.
Chicago
"hallel." In A Dictionary of the Bible. , edited by W. R. F. Browning. Oxford Biblical Studies Online, http://www.oxfordbiblicalcstudies.com/article/opr/t94/e815 (accessed May 19, 2013).