This paper discusses how the rhythmic patterns of Dallapiccola's Sicut Umbra (1970) effectively describe meanings of the text. The piece of Sicut Umbra is a twelve-tone composition for mezzo soprano and twelve instruments. It consists of four movements through which four groups of instruments (three strings, three clarinets, three flutes, and an ensemble of vibraphone, celesta, and harp) are gradually introduced. A different rhythmic pattern is developed in each movement to express efficiently meanings of the text by itself. Furthermore, those four different types of the development of rhythmic patterns design a unique rhythmic form throughout the entire piece corresponding to the text. This paper thus examines how those rhythmic patterns devise a unique rhythmic form throughout the piece yet observe their respective rhythmic patterns and how those rhythm patterns successfully express meanings of the text not only in each movement but also throughout the piece. This analysis introduces some aspects of Dallapiccola's treatment of rhythm as well as of the text within the music and this examination of Sicut Umbra will help to show the profound interconnections found in Dallapiccola's textural setting.