Hadith 3:135
Abu Huraira reported God’s messenger as saying, "If one lies on his wife and compresses her, washing is necessary, even if he does not insert his penis.” (Bukhari and Muslim.)
عَنْ أَبِي هُرَيْرَةَ عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «إِذا جلس بَيْنَ شُعَبِهَا الْأَرْبَعِ ثُمَّ جَهَدَهَا فَقَدْ وَجَبَ الْغسْل وَإِن لم ينزل»
Original Reference: Mishkat al-Masabih 430