It is customary to read the Song of Songs on the first night of Passover at the end of the Seder. In the Diaspora, where the Seder is repeated on the second night of Passover, the reading of this book is sometimes spread over the two nights, but it is more common for the whole book to be completed on the first night.


haggadah Section: Urchatz
Source: http://www.chabad.org/holidays/passover/pesach_cdo/aid/1708/jewish/The-Song-of-Songs.htm