Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) reports this as a marfu' hadith attributed to the Prophet (peace and blessings be upon him), that he (peace and blessings be upon him) said: "Whoever prays four rak'ahs (sunnah) after the Isha prayer in such a way that in the first two rak'ahs he recites Surah al-Kafirun and Surah al-Ikhlas, and in the last two rak'ahs he recites Surah Tanzil al-Sajdah and Surah al-Mulk, this prayer will be recorded for him as being like praying on Laylat al-Qadr (in reward)."
Al-Tabarani recorded it in al-Mu'jam al-Kabir; its chain contains a narrator, Yazid bin Sinan Abu Farwah al-Ruhawi, whom Ahmad, Ali bin al-Madini and Yahya bin Ma'in declared da'if (weak). Al-Bukhari (may Allah have mercy on him) said: "He is muqarib al-hadith (his narrations are passable)." Marwan bin Mu'awiyah declared him thiqah (trustworthy), and Abu Hatim said: "His standing is truthfulness, but there was heedlessness in him."