Narrated Rabi`a: `Umar bin Al-Khattab recited Surat-an-Nahl on a Friday on the pulpit and when he reached the verse of Sajda he got down from the pulpit and prostrated and the people also prostrated. The next Friday `Umar bin Al-Khattab recited the same Sura and when he reached the verse of Sajda he said, O people! When we recite the verses of Sajda (during the sermon) whoever prostrates does the right thing, yet it is no sin for the one who does not prostrate. And `Umar did not prostrate (that day). Added Ibn `Umar Allah has not made the prostration of recitation compulsory but if we wish we can do it.