"Lo Yakhlu LehithMahMeyah" (they were driven out of Egypt and they couldn't delay).  It says in the Gemara of...
Friday, April 2, 2010/Nisan 18, 5770

On the first two days of Pesah (Passover) -- the first day for those in Israel -- we say the complete Hallel....
Sunday, April 12, 2009/Nisan 18, 5769