Look for (and in the words of Waki, seek) Lailat-ul-Qadr in the last ten nights of Ramadan.
Sahih Muslim Book 13, Hadith 282
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I was shown Lailat-ul-Qadr; then I was made to forget it, and saw that I was prostrating in water and clay in the morning of that (night). He (the narrator) said: There was a downpour on the twenty-third night and the Messenger of Allah (ﷺ) led us in prayer, and as he went back, there was a trace of water and clay on his forehead and on his nose. He (the narrator) said: 'Abdullah b. Unais used to say that it was the twenty-third (night).
Sahih Muslim Book 13, Hadith 281 Next Hadith → I thu asked Ubayy b. Ka'b (Allah be pleased with him): Your brother (in faith) Ibn Mas'ud says: He who stands (for the night prayer) throughout the year would find Lailat-ul-Qadr, whereupon he said: May Allah have mercy upon him; (he said these words) with the intention that people might not rely only (on one night), whereas he knew that it (Lailat-ul-Qadr) is in the month of Ramadan and it is the twenty-seventh night. He then took oath (without making any exception, i. e. without saying In sha Allah) that it was the twenty-seventh night. I said to him: Abu Mundhir, on what ground do you say that? Thereupon he said: By the indication or by the sign which the Messenger of Allah (ﷺ) gave us, and that is that on that day (the sun) would rise without having any ray in it.
Sahih Muslim Book 13, Hadith 283
Sahih Muslim Book 13, Hadith 281 Next Hadith → I thu asked Ubayy b. Ka'b (Allah be pleased with him): Your brother (in faith) Ibn Mas'ud says: He who stands (for the night prayer) throughout the year would find Lailat-ul-Qadr, whereupon he said: May Allah have mercy upon him; (he said these words) with the intention that people might not rely only (on one night), whereas he knew that it (Lailat-ul-Qadr) is in the month of Ramadan and it is the twenty-seventh night. He then took oath (without making any exception, i. e. without saying In sha Allah) that it was the twenty-seventh night. I said to him: Abu Mundhir, on what ground do you say that? Thereupon he said: By the indication or by the sign which the Messenger of Allah (ﷺ) gave us, and that is that on that day (the sun) would rise without having any ray in it.
Sahih Muslim Book 13, Hadith 283