In his book, al-Qawlus-Sadeed fee Maqaasid-it- Tawheed Sharhu Kitaab-ut-Tawheed (القول السديد في مقاصيد التوحيد شرح كتاب التوحيد) (which is an Explanation of the Book of the Imaam Muhammad ibn AbdulWahhaab rahimahullaah, Kitaab-ut-Tawheed ),
..the 'Allaamah, 'Abd-ur-Rahmaan ibn Naasir as-Sa'dee rahimahullaah mentions in the commentary of the Chapter 36: "What is said about Riyaa' (showing off)" and Chapter 37: "Intending deeds in the world for the sake of humans is a type of Shirk":
Know that sincerity for Allaah is the foundation of the Religion and the essence of Tawheed and worship. It is when the worshipper intends all of his deeds for the Face of Allaah, for His rewards, and His favours.
So he maintains the six foundations of faith, the five signs of Islaam, and the fulfillment of faith - ihsan - as well as the rights of Allaah and the rights of His worshippers.
In this way his intention is perfected for the Face of Allaah and for the abode of the Hereafter. He does not intend by this to be seen, nor to be heard of, nor does he do it for position, or for worldly matters. By this he will have completed his faith and tawheeed.
Among the worst behaviours that diminish sincerity is to perform deeds just to be seen by people, for their praise, or to honour them, or doing deeds for the sake of worldly matters. This degrades sincerity and tawheed.
Nasheed : Ana Al-Abd Mishary Rashid