Hadith 505210
Chapter 15: The Qur'an - كتاب القرآن
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ عُمَرَ بْنَ الْخَطَّابِ، كَانَ يَقُولُ لاَ تَحَرَّوْا بِصَلاَتِكُمْ طُلُوعَ الشَّمْسِ وَلاَ غُرُوبَهَا فَإِنَّ الشَّيْطَانَ يَطْلُعُ قَرْنَاهُ مَعَ طُلُوعِ الشَّمْسِ وَيَغْرُبَانِ مَعَ غُرُوبِهَا وَكَانَ يَضْرِبُ النَّاسَ عَلَى تِلْكَ الصَّلاَةِ .
Yahya related to me from Malik from Abdullah ibn Dinar from Abdullah ibn Umar that Umar ibn al-Khattab used to say, "Do not intend to do your prayer at either sunrise or sunset, for the horns of Shaytan rise with the rising of the sun and set with its setting." Umar used to beat people for that kind of prayer.
Reference Muwatta Malik 505210
USC-MSA web (English) reference : Book 15, Hadith 49