I only remember some verses about it.
One to save his own life :
16:107 Whoso disbelieves in Allah after he has believed — save him who is forced thereto while his heart finds peace in the faith — but such as open their breasts to disbelief, on them is Allah’s wrath; and they shall have a severe punishment.
Or for a tactic against the ennemy :
8.15 O ye who believe! When ye meet those who disbelieve in battle, turn not your backs to them.
8.16 Whoso on that day turneth his back to them, unless manoeuvring for battle or intent to join a company, he truly hath incurred wrath from Allah, and his habitation will be hell, a hapless journey's end.
Other than for those reasons we can't lie or dissimulate our faith (exept to avoid discriminations).
This is a big sin to lie an to treach on people for money or another reason (except avoiding problems like saying mean things to people like you are ugly, fat etc which only bring problems even if it's true )
8.58 And if thou fearest treachery from any folk, then throw back to them (their treaty) fairly. Lo! Allah loveth not the treacherous.
7.85 Lo! a clear proof hath come unto you from your Lord; so give full measure and full weight and wrong not mankind in their goods, and work not confusion in the earth after the fair ordering thereof. That will be better for you, if ye are believers.
11.84 And give not short measure and short weight. Lo! I see you well-to-do, and lo! I fear for you the doom of a besetting Day.
11.85 O my people! Give full measure and full weight in justice, and wrong not people in respect of their goods. And do not evil in the earth, causing corruption.
83.1 -2 Woe unto the defrauders: Those who when they take the measure from mankind demand it full,
83.3 But if they measure unto them or weight for them, they cause them loss.
83.4 -6 Do such (men) not consider that they will be raised again Unto an awful Day, The day when (all) mankind stand before the Lord of the Worlds?
5.2 (...) And let not your hatred of a folk who (once) stopped your going to the inviolable place of worship seduce you to transgress; but help ye one another unto righteousness and pious duty. Help not one another unto sin and transgression, but keep your duty to Allah. Lo! Allah is severe in punishment.
And there's many other verses and also hadiths like that.