Hadith:

Prophet of Allah صَلَّى اللّٰهُ عَلَيْهِ وَسَلَّم used to observe I'tikaf in the last ten days of Ramadan and used to say: Look for the Night of Qadr in the last ten days of Ramadan.

Sahih Bukhari:2020

Hadith:

Ayesha reported:

At the onset of the last ten days of Ramadan, the Prophet  صَلَّى اللّٰهُ عَلَيْهِ وَسَلَّم used to tighten his waist belt (i.e. worked hard), used to stay up (all night for worship) and wake up his family (for ibadah) too.

Important points according to Sahih Muslim Hadith: 2771:

1.  The Night of Qadr is in Ramadan.
2. Rain is also a sign of Night of Qadr.
3. The first Night of Qadr that our Prophet  صَلَّى اللّٰهُ عَلَيْهِ وَسَلَّم found, was on the 21st night of Ramadan.
4. The Night of Qadr rotates; It does not fall on the 27th night of Ramadan only (or every year).