Hadith on Salat: Know what is being said in prayer

‘Uqbah ibn ‘Amir reported: The Messenger of Allah, peace and blessings be upon him, said, “No Muslim performs ablution and does so thoroughly, then stands for prayer while he knows what he is saying, but that he will return free of any fault like the day he was born from his mother. There will be no sin upon him.

Source: al-Mustadrak 3438

Grade: Sahih (authentic) according to Al-Albani

عَنْ عُقْبَةَ بْنِ عَامِرٍ عَنْ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ مَا مِنْ مُسْلِمٍ يَتَوَضَّأُ فَيُسْبِغُ الْوُضُوءَ ثُمَّ يَقُومُ فِي صَلاتِهِ فَيَعْلَمُ مَا يَقُولُ إِلا انْفَتَلَ كَيَوْمِ وَلَدَتْهُ أُمُّهُ مِنَ الْخَطَايَا لَيْسَ عَلَيْهِ ذَنْبٌ

3438 المستدرك على الصحيحين

546 المحدث الألباني خلاصة حكم المحدث صحيح في صحيح الترغيب