Ziyad related to me from Malik that he had heard that Said ibnal-Musayyab used to say, "Whoever is present at isha on Laylat al-Qadrhas taken his portion from it." (ES)
USC-MSA web (English) reference: Book 19, Hadith 17 (ES)
Arabic reference (ES): Book 19, Hadith 707 (ES)