The Messenger of Allah ﷺ said to us: Seek it (laylat al-Qadr) on the seventeenth night of Ramadan, and on the twenty first night, and on the twenty-third night. He then kept silence. (Using translation from Abū Dāʾūd 1384)
"اطلبُوا ليلَةَ سبْعَ عشرة مِنْ رمضانَ، وليلةَ إحدى وعشرين، وليلةَ ثلاثٍ وعشرينَ".