Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates that the Prophet (peace and blessings be upon him) said: "Whoever offers the Isha prayer in congregation, and offers four rak'ahs before leaving the mosque, it will be equal to (praying on) the Night of Qadr."
Al-Tabarani recorded it in al-Mu'jam al-Kabir; its chain contains a narrator who has been declared da'if (weak) in hadith, and Allah knows best.