Whether we like it or not, others often associate our behavior with the religion we follow. If we behave badly, people may see Islam in a bad light. For example, when so-called "Islamic terrorists"
commit horrible acts, it puts a bad light on the religion (even though terrorists have nothing to do with God's peaceful religion that has come down since Abraham).
On the other hand, when a Muslim observes God's commandments--is truthful, kind and charitable, it reflects positively on the religion.
Of course, God is Omniscient and fully aware of all things (Quran 2:29, 24:64, 33:54, 57:3), He knows everything we conceal and declare (Quran 3:29, 64:4). He knows our innermost thoughts (Quran 2:284, 35:38).
So even if no one else is watching us, we must be on our best behavior because we're at all times in the presence of the Almighty, the Lord of the universe. If we make mistakes, we repent to Him and try harder the next time. So that we may be pleasing to Him and set a good example to the world.
[Quran 26:83] "My Lord, grant me wisdom, and include me with the righteous.
[Quran 26:84] "Let the example I set for the future generations be a good one.
Believers Set the Example
[Quran 49:11] O you who believe, no people shall ridicule other people, for they may be better than they. Nor shall any women ridicule other women, for they may be better than they. Nor shall you mock one another, or make fun of your names. Evil indeed is the reversion to wickedness after attaining faith. Anyone who does not repent after this, these are the transgressors.
May God help us be on our best behavior today and each day.
Al Qur'an 98:5
"All that was asked of them was to worship GOD,
devoting the religion absolutely to Him alone,
observe the contact prayers (Salat), and give the obligatory charity (Zakat).
Such is the perfect religion."