From Fiqh Sunnah – Sayyid Sabiq
The night of qadr is the most virtuous night of the year. Allah says in the al-Quran : ‘We revealed it on the night of power [that is qadr]. What will tell you what the night of power is? It is better than a thousand months.”
Al-Bukhari and Muslim recorded form Abu Hurairah that the Prophet , upon whom be peace, said :“whoever prays during the night of Qadr in faith and hoping for its reward will have all his previous sins forgiven.”
As for the supplication during the night of qadr, Aishah R.A said : ‘I asked the Messenger of Allah: “ O Messenger of Allah, if I know what night is the night of qadr, what should I say during it?’ He said ‘ Say: o Allah, You are pardoning and You love to pardon, so pardon me’” This is related by Ahmad, Ibn Majah and by at-Tirmizhi, who called it sahih.