Citing your sources is required. Not citing sources is plagiarism.
Citing demonstrates that you have consulted other sources, points your readers to those sources, and gives credit to others whose ideas you have used. You must cite whether quoting directly (word for word) or paraphrasing others' ideas. Understanding academic dishonesty and what constitutes plagiarism is your responsibility. The consequences for not citing sources correctly are serious and can include disciplinary action. Correct citation includes:
Think plagiarism is just an issue for college students writing research papers? Think again! Check out these real world examples of celebrities being accused of plagiarizing.