It's not uncommon for us humans to be tempted over impure thoughts. Impurity is a lust for anything outside that which God has blessed- a relationship between man and woman in a marriage.
Many people are bound in lusts and desires and these have a tight hold on them. But it does not mean that we have to remain that way. Just like any other sin, we have to fight against it to overcome it.
Thus, here's a list of powerful Bible verses that can be used as a weapon when we are tempted to impurity.
"There is no one greater in this house than I, nor has he kept back anything from me but you, because you are his wife. How then can I do this great wickedness, and sin against God?"
"You have heard it said of old, 'You shall not commit adultery.' But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart. If your right eye causes you to sin, pluck it out and cast it from you; for it is more profitable for you that one of your members perish, than for your whole body to be cast into hell."
"I have made a covenant with my eyes; Why then should I look upon a young woman?"
"Then He said to them all, 'If anyone desires to come after Me, let him deny himself, and take up his cross daily, and follow Me.'"
"What shall we say then? Shall we continue in sin that grace may abound? Certainly not! How shall we who died to sin live any longer in it?"
"'Father, if it is Your will, take this cup away from Me; nevertheless not My will, but Yours, be done.'"
2 Corinthians 7:1
"Therefore, having these promises, beloved, let us cleanse ourselves from all filthiness of the flesh and spirit, perfecting holiness in the fear of God."