✅ Answer: There are two possible scenarios for the above question:

✅ If you doubt whether you have performed ruku' while still standing, follow the narration below:

عَنْ فَضَالَةَ عَنْ حُسَیْنٍ وَ مُحَمَّدِ بْنِ سِنَانٍ جَمِیعاً عَنِ ابْنِ مُسْکَانَ عَنْ أَبِی بَصِیرٍ قَالَ سَأَلْتُ أَبَا عَبْدِ اللَّهِ عَنْ رَجُلٍ شَکَّ وَ هُوَ قَائِمٌ فَلَا یَدْرِی أَ رَکَعَ أَمْ لَمْ یَرْکَعْ قَالَ یَرْکَعُ وَ یَسْجُدُ

📚 Al-Tahdhib, vol. 2, p. 150

Translation: Abi Basir said: I asked Imam Sadiq (peace be upon him) about a person who doubts while standing whether they have performed ruku'. The Imam said: Perform the ruku' and then the sajdah.

This means that if you are still within the standing position and doubt whether you performed the ruku' and need to go to sajdah or have not yet performed the ruku', you should perform the ruku'.

✅ In the second scenario, if you have moved past the ruku' position and have gone to sajdah or beyond and then doubt whether you performed the ruku', follow the narration below:

عَنْ صَفْوَانَ عَنِ ابْنِ بُکَیْرٍ عَنْ مُحَمَّدِ بْنِ مُسْلِمٍ عَنْ أَبِی جَعْفَرٍ قَالَ کُلُّ مَا شَکَکْتَ فِیهِ مِمَّا قَدْ مَضَی فَامْضِهِ کَمَا هُوَ

📚 Al-Tahdhib, vol. 2, p. 344

Translation: Imam Baqir (peace be upon him) said: Whatever you doubt about from those things (whose place) has passed, pass it as it is (do not pay attention to it).

✅ This means if you have moved past the place (of ruku') and then doubt, pass it and do not pay attention to it.

✅ Also, pay attention to the following narration:

عَنْ زُرَارَةَ قَالَ قُلْتُ لِأَبِی عَبْدِ اللَّهِ رَجُلٌ شَکَّ فِی الْأَذَانِ وَ قَدْ دَخَلَ فِی الْإِقَامَةِ قَالَ یَمْضِی قُلْتُ رَجُلٌ شَکَّ فِی الْأَذَانِ وَ الْإِقَامَةِ وَ قَدْ کَبَّرَ قَالَ یَمْضِی قُلْتُ رَجُلٌ شَکَّ فِی التَّکْبِیرِ وَ قَدْ قَرَأَ قَالَ یَمْضِی قُلْتُ شَکَّ فِی الْقِرَاءَةِ وَ قَدْ رَکَعَ قَالَ یَمْضِی قُلْتُ شَکَّ فِی الرُّکُوعِ وَ قَدْ سَجَدَ قَالَ یَمْضِی عَلَی صَلَاتِهِ ثُمَّ قَالَ یَا زُرَارَةُ إِذَا خَرَجْتَ مِنْ شَیْ ءٍ ثُمَّ دَخَلْتَ فِی غَیْرِهِ فَشَکُّکَ لَیْسَ بِشَیْ ءٍ

📚 Al-Tahdhib, vol. 2, p. 352

Translation: Zurara said: I asked Imam Sadiq (peace be upon him): A person doubts in the adhan while starting the iqamah, what should they do? He said: Pass it. I said: A person doubts in the adhan and iqamah while saying the takbirat al-ihram; he said: Pass it. I said: A person doubts in the takbirat al-ihram while starting the recitation; he said: Pass it. I said: A person doubts in the recitation while performing the ruku'; he said: Pass it. I said: A person doubts in the ruku' while performing the sajdah; he said: Pass it in your prayer and do not pay attention to it. Then he said: O Zurara, when you have moved past something and then entered something else in the prayer, your doubt is nothing (it is not considered, and do not pay attention to it).