✅Answer: In the case where a person forgets to say the dhikr of ruku' and sujood, pay attention to the following two narrations:

1 عَنْ مُحَمَّدِ بْنِ أَحْمَدَ بْنِ يَحْيَى عَنْ جَعْفَرِ بْنِ مُحَمَّدٍ عَنْ عَبْدِ اللَّهِ الْقَدَّاحِ عَنْ جَعْفَرٍ عَنْ أَبِيهِ أَنَّ عَلِيّاً سُئِلَ عَنْ رَجُلٍ رَكَعَ وَ لَمْ يُسَبِّحْ نَاسِياً قَالَ تَمَّتْ صَلَاتُهُ.

📚 Al-Tahdheeb, Vol. 2, p. 157

Imam Sadiq (peace be upon him) narrated from his father that Ali (peace be upon him) was asked about a person who performed ruku' but forgot to say the tasbih; he said: His prayer is complete!

2 عَنْ عَلِيِّ بْنِ يَقْطِينٍ قَالَ: سَأَلْتُ أَبَا الْحَسَنِ الْأَوَّلَ عَنْ رَجُلٍ نَسِيَ تَسْبِيحَهُ فِي رُكُوعِهِ وَ سُجُودِهِ قَالَ لَا بَأْسَ بِذَلِكَ.

2 Al-Tahdheeb, Vol. 2, p. 157

Ali ibn Yaqtin said: I asked Imam Kazim (peace be upon him) about a person who forgets his tasbih in his ruku' and sujood; the Imam said: There is no problem.

✅But if a person intentionally leaves out the dhikr and tasbih of ruku' and sujood, pay attention to the following narration:

3 عَنْ أَحْمَدَ بْنِ مُحَمَّدِ بْنِ عِيسَى عَنْ عَلِيِّ بْنِ الْحَكَمِ عَنْ عُثْمَانَ بْنِ عَبْدِ الْمَلِكِ عَنْ أَبِي بَكْرٍ الْحَضْرَمِيِّ قَالَ: قُلْتُ لِأَبِي جَعْفَرٍ أَيُّ شَيْ ءٍ حَدُّ الرُّكُوعِ وَ السُّجُودِ قَالَ تَقُولُ سُبْحَانَ رَبِّيَ الْعَظِيمِ وَ بِحَمْدِهِ ثَلَاثاً فِي الرُّكُوعِ وَ سُبْحَانَ رَبِّيَ الْأَعْلَى وَ بِحَمْدِهِ ثَلَاثاً فِي السُّجُودِ فَمَنْ نَقَصَ وَاحِدَةً نَقَصَ ثُلُثَ صَلَاتِهِ وَ مَنْ نَقَصَ اثْنَتَيْنِ نَقَصَ ثُلُثَيْ صَلَاتِهِ وَ مَنْ لَمْ يُسَبِّحْ فَلَا صَلَاةَ لَهُ.

📚 Al-Tahdheeb, Vol. 2, p. 80

Abu Bakr al-Hadrami said: I said to Imam Baqir (peace be upon him): What is the minimum for ruku' and sujood? He said: Three times in ruku' you say:

سُبْحَانَ رَبِّيَ الْعَظِيمِ وَ بِحَمْدِهِ

And three times in sujood you say:

سُبْحَانَ رَبِّيَ الْأَعْلَى وَ بِحَمْدِهِ

So he who makes one of them deficient (meaning he says the tasbih twice in ruku' and sujood), has made one-third of his prayer deficient, and he who reduces two of them (meaning he says the tasbih once), has made two-thirds of his prayer deficient, and he who does not say the tasbih at all, there is no prayer for him (his prayer is invalid)!

✅ Also, regarding a person who doubts whether he said the dhikr and tasbih in ruku' and sujood or not, pay attention to the following narration:

4 عَنْ عَبْدِ اللَّهِ بْنِ الْحَسَنِ عَنْ جَدِّهِ عَلِيِّ بْنِ جَعْفَرٍ عَنْ أَخِيهِ مُوسَى بْنِ جَعْفَرٍ قَالَ: سَأَلْتُهُ عَنْ رَجُلٍ رَكَعَ وَ سَجَدَ وَ لَمْ يَدْرِ هَلْ كَبَّرَ أَوْ قَالَ شَيْئاً فِي رُكُوعِهِ وَ سُجُودِهِ هَلْ يَعْتَدُّ بِتِلْكَ الرَّكْعَةِ وَ السَّجْدَةِ قَالَ إِذَا شَكَّ فَلْيَمْضِ فِي صَلَاتِهِ.

4 Qurb al-Isnad, p. 91

Ali ibn Ja'far said: I asked Musa ibn Ja'far (peace be upon him) about a person who has performed ruku' and sujood and does not know whether he said the takbir or said anything in his ruku' and sujood or not, should he count that ruku' and sujood or not? The Imam said: If he is in doubt, he should continue his prayer (and not pay attention).

✅ From the totality of the above narrations, it is clear that:

1 A person who forgets to say the dhikr and tasbih of ruku' and sujood, nothing is on him and his prayer is complete.

2 A person who intentionally does not say the dhikr and tasbih in ruku' and sujood, there is no prayer for him.

3 A person who doubts whether he said the dhikr and tasbih in ruku' and sujood or not, he should continue his prayer and not pay attention.

✅ Let us learn the words and sayings of the Ahl al-Bayt (peace be upon them) and act upon them so that the sentence we utter in the Ziyarat Jamia Kabira, addressing the Imam (peace be upon him), is based on truth:

آخِذٌ بِقَوْلِکُمْ عَامِلٌ بِأَمْرِکُمْ

Translation: I take your saying and word and I act upon your command!

اللَّهُمَّ فَصَلِّ عَلَی مُحَمَّدٍ وَ آلِ مُحَمَّدٍ وَ عَجِّلْ لِوَلِیِّکَ الْفَرَجَ وَ الْعَافِیَةَ وَ النَّصْرَ