Abd al-Rahman bin Yazid (may Allah have mercy on him) said: There was an hour in which, whenever I came to Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him), I found him praying in it, (namely) between Maghrib and Isha. So I asked Sayyiduna Abdullah (may Allah be pleased with him): Whenever I come to you (at this time), I find you praying. He said: "It is the hour of heedlessness."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9417