Allaah says in his final revelation, the Qur'aan:

"Therefore turn your face steadfastly towards the true faith, away from all that which is false, in accordance with the Pure nature with which Allaah has Created people. Let there be no altering in the laws of Allaah's Creation. This is surely the true religion, but most people do not know it."
(Surah Ar-Rum 30:30)

"And whatever of blessings and good things you have, it is from Allah. Then, when harm touches you, unto him you cry aloud for help. Yet no sooner does he remove your ills then some of you set up partners to their lord."
(Surah An-Nahl 16:53-54)

Allaah says in the Qur'aan:
"Verily in the creation of the heavens and the earth, in the alternation of night and day, in the sailing of the ships through the ocean for the profit of the people, in the water which Allaah sends down from the skies reviving with it the dead earth and dispersing over it all kinds of beasts, in the change of the winds, and in the clouds that run their appointed courses between heaven and earth: In all of this, indeed there are signs for people of understanding."
(Surah Al-Baqarah 2:164)

"Blessed be He to Whom all sovereignty belongs; He has power over all things. He Who Created death and life that He may test which of you is best in deed. He is the Almighty, the Oft-forgiving. He Who Created the seven heavens one above another. You can see no fault in the Creation of the Bestower of Mercy. Turn up your eyes: Can you detect a single flaw? Look once more, and yet again: Your sight will in the end grow humbled and weary."
(Surah Al-Mulk 67:1-4)

"On the earth are signs visible to all who have faith with certainty, just as there are signs within your ownselves. Will you then not see?"
(Surah Adh-Dhariyat 51:20-21)

"Were they created of nothing? or were they perchance, their own creators? or did they create the heavens and the earth? surely they have no firm belief."
(Surah At-Tur 52:35-36)