Halakhah su Salmi 118:25

Repetition of complete verses of the psalms is, however, significantly different in nature. The meaning of the sentences uttered is not distorted by means of repetition. Since the psalms are not blessings, but are designed to extol the praises of God, repetition does not appear to constitute a hefsek. Indeed, the verses of Psalms 118:25-29 are regularly repeated in the course of hallel for reasons advanced by Rashi, Sukkah 38a. Similarly, Psalms 150:6 is repeated in the daily morning service to indicate that it constitutes the final verse of the section referred to in Shabbat 118b as "hallel."