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.  

لَنَا رَسُولُ اللَّهِ ﷺ اطْلُبُوهَا لَيْلَةَ سَبْعَ عَشْرَةَ مِنْ رَمَضَانَ وَلَيْلَةَ إِحْدَى وَعِشْرِينَ وَلَيْلَةَ ثَلاَثٍ وَعِشْرِينَ ثُمَّ سَكَتَ