He who truly knows Allah will love Him, worship Him and show Ikhlass (sincerity) towards Him.
Ikhlass (sincerity) is like Jannah (Heaven) for a Mu"men. It is the soul of the pious and a secret between Allah and His slave. Ikhlass thwarts evil thoughts and Shaytan"s (Satan) whispers to the slave. It means directing all of your actions to Allah and no one else. The Mu"men must not seek the pleasure of anything or anyone except Allah. He must never seek praise or tributes from people, but always expect rewards from only Him alone.
An example of pure ikhlass can be seen in the actions of Ayoub As-Sakhtiyani who used to perform Salah all night long. He did not tell any body about it and when the morning came, he used to act as if he had just woken up from sleep.
To have Ikhlass means one perfects and completes an action in the best manner possible. It is the dearest trait in this world. It is to single out Allah with your intention when carrying out acts of worship through continuously observing only Allah alone. What is done for Allah"s sake alone is rewarded, but what is done for others beside Allah goes in vain and is lost into thin air. The Prophet (peace be upon him) said: "The reward of deeds depend upon the intentions and every person will get the reward according to what he has intended. So whoever emigrates for worldly benefits or for a woman to marry, his emigration will be for what he emigrated for" (Narrated by al-Bukhari).