Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
bayhaqi:5465ʿĀṣim

[Machine] Seventeen prayers are shortened, so whoever performs seventeen prayers shortens them, and whoever performs more than that completes them. Abu Amr al-Bastami, the scholar, informed us. Abu Bakr al-Isma'ili narrated to me. Al-Hasan, the son of Sufyan, informed me. Muhammad ibn Abdullah ibn Numair informed me. Hafs mentioned him.  

البيهقي:٥٤٦٥وَرَوَاهُ حَفْصُ بْنُ غِيَاثٍ عَنْ عَاصِمٍ فَقَالَ

سَبْعَ عَشْرَةَ يَقْصُرُ الصَّلَاةَ فَمَنْ أَقَامَ سَبْعَ عَشْرَةَ قَصَرَ وَمَنْ أَقَامَ أَكْثَرَ مِنْ ذَلِكَ أَتَمَّ أَخْبَرَنَا أَبُو عَمْرٍو الْبَسْطَامِيُّ اْلْأَدِيبُ ثنا أَبُو بَكْرٍ الْإِسْماعِيلِيُّ أَخْبَرَنِي الْحَسَنُ هُوَ ابْنُ سُفْيَانَ ثنا مُحَمَّدُ بْنُ عَبْدِ اللهِ بْنِ نُمَيْرٍ ثنا حَفْصٌ فَذَكَرَهُ