Hadith 430
عَنْ أَبِي هُرَيْرَةَ عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «إِذا جلس بَيْنَ شُعَبِهَا الْأَرْبَعِ ثُمَّ جَهَدَهَا فَقَدْ وَجَبَ الْغسْل وَإِن لم ينزل»
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.)