Translation:

1. Sad. By the Qur'an full of Admonition: (this is the Truth).

Notes (Tafseer)

4146. Sad is a letter of the Arabic alphabet. It is used here as an Abbreviated Letter, for which see Appendix I (at the end of Sura ii.). See also the second para, of n. 989 to vii. I for this particular letter. No dogmatism is permissible in trying to interpret Abbreviated Letters. This Sura is concerned mainly with the stories of David and Solomon as illustrative of the relative positions of spiritual and worldly power. Sale's note: "it may stand for Solomon": is a real howler; for in Arabic the letter Sad does not occur at all in the name of Solomon.

4147. Full of admonition: the word zikr is far more comprehensive than any single word or phrase that I can think of in English: it implies (1) remembrance in a spirit of reverence; (2) recital, celebrating the praises of Allah; (3) teaching, admonition, warning; (4) Message, Revelation, as in Ah-luz-zikr, "those who possess the Message" (xvi. 43, and n. 2069). Devotional exercises are also called zikr, with reference to meaning (2) above.