from 'Ubayy bin Ka'b, that the Prophet (ﷺ) would recite: "Qad Balaghta Min Ladunni 'Udhra" (18:76) with heaviness (Muthaqqalah - meaning with Tashdid on the Nun in "Ladunni")."
Jami` at-Tirmidhi Book 46, Hadith 7