Complex sentence: Eleazar ben Killir (c.570--c.640) was a Hebrew poet whose classical liturgical verses, known as piyut, have continued to be sung through the centuries during significant religious services, including those on Tisha B'Av and on the sabbath after a wedding.
Split into simpler sentences: Eleazar ben Killir (c.570--c.640) was a Hebrew poet notable as a composer of classical liturgical poetry known as piyut. His piyut are sung in many liturgical services, including those on Tisha B'Av and on the sabbath after a wedding.