If one may not say tehillim at night, why did King Dovid? As related in begining of Gemara Brochos. Saying Tehilim after shkia
Rabbi Avraham David Wahrman of Buczacz says that the law of reading tehillim should be like Torah Shel B'al peh. He cites the Midrash which describes King David as requesting from the Almighty that his Psalms be granted unique status. People should not read Psalms as they read other works of literature. Rather, Psalms should be read and pondered. Moreover, readers of Psalms should receive reward as if they were studying difficult passages of the Oral Law that deal with ritual purity (Midrash Shoher Tov 1:8). but many do disagree with him. However, Rabbi Hayim Elazar Shapiro of Munkacs (1871-1937) was aware of what Rabbi Avraham David of Buczacz had written, but he saw the extrapolation from the Midrash as problematic.