Hadith 3:13
Jabir reported God’s messenger as saying, “The key of paradise is prayer, and the key of prayer is being purified." Ahmad transmitted it.
عَنْ جَابِرٍ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «مِفْتَاحُ الْجَنَّةِ الصَّلَاةُ وَمِفْتَاحُ الصَّلَاة الطّهُور» . رَوَاهُ أَحْمد
Original Reference: Mishkat al-Masabih 294