Mu'adh bin Anas Al-Juhani (May Allah be pleased with him) said:
The Prophet (ﷺ) forbade (us) from sitting with our legs drawn up to our belly (Ihtiba') during the Friday Khutbah (religious talk before the prayer).[Abu Dawud and At-Tirmidhi].
App reference: Book 18, Hadith 195
Arabic/English book reference: Book 18, Hadith 1705