✅Answer: First, pay attention to the limit of bowing and prostration in the following narration:

عَنْ أَبِی بَکْرٍ الْحَضْرَمِیِّ قَالَ قُلْتُ لِأَبِی جَعْفَرٍ أَیُّ شَیْ ءٍ حَدُّ الرُّکُوعِ وَ السُّجُودِ قَالَ تَقُولُ سُبْحَانَ رَبِّیَ الْعَظِیمِ وَ بِحَمْدِهِ ثَلَاثاً فِی الرُّکُوعِ وَ سُبْحَانَ رَبِّیَ الْأَعْلَی وَ بِحَمْدِهِ ثَلَاثاً فِی السُّجُودِ فَمَنْ نَقَصَ وَاحِدَةً نَقَصَ ثُلُثَ صَلَاتِهِ وَ مَنْ نَقَصَ اثْنَتَیْنِ نَقَصَ ثُلُثَیْ صَلَاتِهِ وَ مَنْ لَمْ یُسَبِّحْ فَلَا صَلَاةَ لَهُ

📚Al-Kafi, Vol. 3, p. 329

Translation: Al-Hadhrami said: 'I said to Imam Baqir (peace be upon him): 'What is the limit of bowing and prostration?' He said: 'In bowing, you say three times:

سُبْحَانَ رَبِّیَ الْعَظِیمِ وَ بِحَمْدِهِ

And three times in prostration you say:

سُبْحَانَ رَبِّیَ الْأَعْلَی وَ بِحَمْدِهِ

So whoever reduces one of them has made his prayer deficient by one-third, and whoever reduces two of them has made his prayer deficient by two-thirds, and whoever does not say any glorification (in bowing and prostration), there is no prayer for him.'

✅The above narration defines the limit of bowing and prostration for someone who wants to perform it completely. But according to the following narration, one complete and full glorification is also sufficient, although the value and reward of the prayer are reduced according to the above narration:

عَنْ زُرَارَةَ عَنْ أَبِی جَعْفَرٍ قَالَ قُلْتُ لَهُ مَا یُجْزِی مِنَ الْقَوْلِ فِی الرُّکُوعِ وَ السُّجُودِ فَقَالَ ثَلَاثُ تَسْبِیحَاتٍ فِی تَرَسُّلٍ وَ وَاحِدَةٌ تَامَّةً تُجْزِی

📚Al-Tahdhib, Vol. 2, p. 76

Translation: Zurarah said: 'I said to Imam Baqir (peace be upon him): 'What words are sufficient in bowing and prostration?' The Imam said: 'Three glorifications with deliberation and tranquility, and one complete and full glorification is also sufficient.'

عَنْ مُعَاوِیَةَ بْنِ عَمَّارٍ قَالَ قُلْتُ لِأَبِی عَبْدِ اللَّهِ أَخَفُّ مَا یَکُونُ مِنَ التَّسْبِیحِ فِی الصَّلَاةِ قَالَ ثَلَاثُ تَسْبِیحَاتٍ مُتَرَسِّلًا تَقُولُ سُبْحَانَ اللَّهِ سُبْحَانَ اللَّهِ سُبْحَانَ اللَّهِ

📚Al-Tahdhib, Vol. 2, p. 77

Mu'awiyah ibn Ammar said: 'I said to Imam Sadiq (peace be upon him): 'What is the lightest glorification in prayer?' The Imam said: 'Three glorifications with deliberation and tranquility, you say:

سُبْحَانَ اللَّهِ سُبْحَانَ اللَّهِ سُبْحَانَ اللَّهِ

عَنْ أَبِی عَبْدِ اللَّهِ قَالَ أَدْنَی التَّسْبِیحِ ثَلَاثُ مَرَّاتٍ وَ أَنْتَ سَاجِدٌ لَا تَعْجَلْ بِهِنَّ

📚Al-Tahdhib, Vol. 2, p. 80

Imam Sadiq (peace be upon him) said: 'The minimum glorification in prostration is three times, and you should not be in a hurry in saying them.'

✅So, according to the above narrations, one complete and full glorification or three times 'Subhan Allah' is sufficient for prostration and bowing, and the prayer is valid, but it reduces the value and reward of the prayer, and saying three complete and full glorifications is its limit. However, the Ahl al-Bayt (peace be upon them) have strongly recommended prolonging bowing and prostration:

عَنْ أَبَانِ بْنِ تَغْلِبَ قَالَ دَخَلْتُ عَلَی أَبِی عَبْدِ اللَّهِ وَ هُوَ یُصَلِّی فَعَدَدْتُ لَهُ فِی الرُّکُوعِ وَ السُّجُودِ سِتِّینَ تَسْبِیحَةً

📚Al-Kafi, Vol. 3, p. 329

Aban said: 'I entered upon Imam Sadiq (peace be upon him) while he was praying, and I counted that he said the glorification sixty times in bowing and prostration.'

عَنْ زُرَارَةَ قَالَ سَمِعْتُ أَبَا عَبْدِ اللَّهِ یَقُولُ ثَلَاثَةٌ إِنْ تَعَلَّمَهُنَّ الْمُؤْمِنُ کَانَتْ زِیَادَةً فِی عُمُرِهِ وَ بَقَاءَ النِّعْمَةِ عَلَیْهِ فَقُلْتُ وَ مَا هُنَّ فَقَالَ تَطْوِیلُهُ فِی رُکُوعِهِ وَ سُجُودِهِ فِی صَلَاتِهِ وَ تَطْوِیلُهُ لِجُلُوسِهِ عَلَی طَعَامِهِ إِذَا طَعِمَ عَلَی مَائِدَتِهِ وَ اصْطِنَاعُهُ الْمَعْرُوفَ إِلَی أَهْلِهِ

📚Al-Kafi, Vol. 4, p. 50

Zurarah said: 'I heard Imam Sadiq (peace be upon him) say: 'There are three things that if a believer knows them, they will increase his lifespan and keep the blessings on him.' I said: 'What are they?' He said: 'Prolonging his bowing and prostration, and prolonging his sitting over food when he eats at the table, and being kind to his family.'

✅It is clear that although saying one complete glorification, i.e., 'Subhana Rabbiyal A'la wa bi-hamdih,' or saying 'Subhan Allah' three times is sufficient in bowing and prostration, the Ahl al-Bayt (peace be upon them) have specified its limit as three complete glorifications and have strongly recommended prolonging bowing and prostration in several hadiths.