Bible Verses About Skepticism: General references

What is the Almighty, that we should serve him? And what profit should we have, if we pray unto him?

Who said unto God, Depart from us; And, What can the Almighty do for us?

The fool hath said in his heart, There is no God. They are corrupt, they have done abominable works; There is none that doeth good.

The fool hath said in his heart, There is no God. Corrupt are they, and have done abominable iniquity; There is none that doeth good.

And it shall come to pass at that time, that I will search Jerusalem with lamps; and I will punish the men that are settled on their lees, that say in their heart, Jehovah will not do good, neither will he do evil.

Ye have said, It is vain to serve God; and what profit is it that we have kept his charge, and that we have walked mournfully before Jehovah of hosts?