[Machine] The Prophet ﷺ used to remain silent when he entered prayer and when he finished reciting. Imran ibn Husayn disapproved of this and they wrote to Ubay ibn Ka'b. He replied to them saying that Samurah was telling the truth. Abu Muhammad says Qatadah used to say three silences, and in the raised narration, there are two silences.  

أَنَّ رَسُولَ اللَّهِ ﷺ كَانَ يَسْكُتُ سَكْتَتَيْنِ إِذَا دَخَلَ فِي الصَّلَاةِ وَإِذَا فَرَغَ مِنَ الْقِرَاءَةِ فَأَنْكَرَ ذَلِكَ عِمْرَانُ بْنُ حُصَيْنٍ فَكَتَبُوا إِلَى أُبَيِّ بْنِ كَعْبٍ فَكَتَبَ إِلَيْهِمْ أَنْ قَدْ صَدَقَ سَمُرَةُ قَالَ أَبُو مُحَمَّدٍ كَانَ قَتَادَةُ يَقُولُ ثَلَاثُ سَكَتَاتٍ وَفِي الْحَدِيثِ الْمَرْفُوعِ سَكْتَتَانِ  

The Messenger of Allah ﷺ kept silence between the takbir and the recitation of Qur’an. So I asked him, for whom I would give my father and mother as ransom: What do you say during you period of silence between the takbir and the recitation? He replied (that he said): O Allah, purify me from sins as a white garment is purified from filth. O Allah, wash away my sings with snow, water and hail. (Using translation from Abū Dāʾūd 781)   

كَانَ رَسُولُ اللَّهِ ﷺ يَسْكُتُ بَيْنَ التَّكْبِيرِ وَالْقِرَاءَةِ إِسْكَاتَةً حَسِبْتُهُ قَالَ هُنَيَّةً فَقُلْتُ لَهُ بِأَبِي وَأُمِّي يَا رَسُولَ اللَّهِ أَرَأَيْتَ إِسْكَاتَتَكَ بَيْنَ التَّكْبِيرِ وَالْقِرَاءَةِ مَا تَقُولُ؟ قَالَ أَقُولُ «اللَّهُمَّ بَاعِدْ بَيْنِي وَبَيْنَ خَطَايَايَ كَمَا بَاعَدْتَ بَيْنَ الْمَشْرِقِ وَالْمَغْرِبِ اللَّهُمَّ نَقِّنِي مِنْ خَطَايَايَ كَمَا يُنَقَّى الثَّوْبُ الْأَبْيَضُ مِنَ الدَّنَسِ اللَّهُمَّ اغْسِلْنِي مِنْ خَطَايَايَ بِالثَّلْجِ وَالْمَاءِ الْبَارِدِ»