✅ Answer: Please pay attention to the following narration:

مُحَمَّدُ بْنُ عَلِیِّ بْنِ الْحُسَیْنِ بِإِسْنَادِهِ عَنْ مُحَمَّدِ بْنِ مُسْلِمٍ عَنْ أَبِی عَبْدِ اللَّهِ أَنَّهُ قَالَ إِنْ شَکَّ الرَّجُلُ بَعْدَ مَا صَلَّی فَلَمْ یَدْرِ أَ ثَلَاثاً صَلَّی أَمْ أَرْبَعاً وَ کَانَ یَقِینُهُ حِینَ انْصَرَفَ أَنَّهُ کَانَ قَدْ أَتَمَّ لَمْ یُعِدِ الصَّلَاةَ وَ کَانَ حِینَ انْصَرَفَ أَقْرَبَ إِلَی الْحَقِّ مِنْهُ بَعْدَ ذَلِکَ

📚 Man La Yahduruhu al-Faqih, Vol. 1, p. 352

Translation: Imam Sadiq (peace be upon him) said: If a person doubts after completing their prayer and is uncertain whether they prayed three or four rak'ahs, and when giving the Salaam they were certain their prayer was complete, they do not need to repeat the prayer. The certainty they had when giving the Salaam is closer to the truth than any doubt that arises afterward.

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