Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
suyuti:3411a –

“Seek Lailatul-Qadr in the last ten nights of Ramadan, and if you miss anything, make sure you do not miss the last seven nights.ʿ (Using translation from Aḥmad 1111)   

السيوطي:٣٤١١a –

"اطلبُوا ليلةَ القدرِ في الْعشرِ الأَوَاخِرِ؛ فإِنْ غُلبِتْمُ فلا تُغْلَبُوا في السَّبْعِ الْبَوَاقِي".  

[عم] زيادات عبد الله بن أحمد عن علي

See similar narrations below:

Collected by Aḥmad
ahmad:1111 – ʿAbdullāh > Sūwayd b. Saʿīd > ʿAbd al-Ḥamīd b. al-Ḥasan al-Hilālī > Abū Isḥāq > Hubayrah b. Yarīm > ʿAlī

“Seek Lailatul-Qadr in the last ten nights of Ramadan, and if you miss anything, make sure you do not miss the last seven nights.ʿ  

أحمد:١١١١ – حَدَّثَنَا عَبْدُ اللهِ حَدَّثَنِي سُوَيْدُ بْنُ سَعِيدٍ أَخْبَرَنِي عَبْدُ الْحَمِيدِ بْنُ الْحَسَنِ الْهِلالِيُّ عَنْ أَبِي إِسْحَاقَ عَنْ هُبَيْرَةَ بْنِ يَرِيمَ عَنْ عَلِيٍّ

أَنَّ رَسُولَ اللهِ ﷺ قَالَ اطْلُبُوا لَيْلَةَ الْقَدْرِ فِي الْعَشْرِالْأَوَاخِرِ مِنْ رَمَضَانَ فَإِنْ غُلِبْتُمْ فَلا تُغْلَبُوا عَلَى السَّبْعِ الْبَوَاقِي