✅ Answer: Please refer to the following narrations:

1⃣عَنِ الْحُسَیْنِ بْنِ سَعِیدٍ عَنِ الْقَاسِمِ بْنِ مُحَمَّدٍ عَنْ رَجُلٍ عَنْ أَبِی بَصِیرٍ عَنْ أَبِی عَبْدِ اللَّهِ قَالَ: إِذَا رَفَعْتَ رَأْسَکَ مِنَ الرُّکُوعِ فَأَقِمْ صُلْبَکَ فَإِنَّهُ لَا صَلَاةَ لِمَنْ لَا یُقِیمُ صُلْبَهُ.

📚 Al-Kafi, Vol. 3, p. 320

Imam Sadiq (peace be upon him) said: When you raise your head from the bowing, straighten your spine and back, because there is no prayer for anyone who does not straighten their back and spine!

2⃣ عَنْ أَبِی بَصِیرٍ عَنْ أَبِی عَبْدِ اللَّهِ في حديث قَالَ: إِذَا رَفَعْتَ رَأْسَکَ مِنَ الرُّکُوعِ فَأَقِمْ صُلْبَکَ حَتَّی تَرْجِعَ مَفَاصِلُکَ.

📚 Al-Tahdhib, Vol. 2, p. 325

Imam Sadiq (peace be upon him) said in a narration: When you raise your head from the bowing, straighten your back and spine so that your joints return to their place!

✅ Based on the above narrations and others, the person praying must completely straighten their back and spine after performing the bowing and stand completely upright.

اللَّهُمَّ صَلِّ عَلَی مُحَمَّدٍ وَ آلِ مُحَمَّدٍ وَ عَجِّلْ لِوَلِیِّکَ الْفَرَجَ وَ الْعَافِیَةَ وَ النَّصْر

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