(4) Prayer
كتاب الصلاة
(15c) Chapter: Prostration and its Excellence - Section 3
(14) باب السجود وفضله - الفصل الثالث
Mishkat al-Masabih 904 
Talq b. ‘Ali al-Hanafi reported God’s Messenger as saying, “God does not regard the prayer of a servant who does not straighten his spine between his bowing and his prostration.” Ahmad transmitted it.
وَعَن طلق بن عَليّ الْحَنَفِيّ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «لَا يَنْظُرُ اللَّهُ عَزَّ وَجَلَّ إِلَى صَلَاةِ عَبْدٍ لَا يُقِيمُ فِيهَا صُلْبَهُ بَيْنَ ركوعها وسجودها» . رَوَاهُ أَحْمد
 صَحِيح  (الألباني)حكم :
Reference : Mishkat al-Masabih 904
In-book reference : Book 4, Hadith 328