One must be resolute in refraining from falsehood in his speech, whether the lie is large or small, explicit or implicit.

Rabbi Elazar said: Anyone who alters the truth in his speech, it is as though he worships idols.

Shmuel said: It is prohibited to deceive people, even to deceive a gentile.

Rabbi Zeira said: A person should not say to a child: I will give you something, and not give it to him, because he thereby teaches the child to lie.

This is the punishment of the liar: Even if he speaks the truth, people do not listen to him. (Sanhedrin 92a; Ĥullin 94b; Sukka 46b; Sanhedrin 89b)