Did you fast in the middle of Sha'ban? He said: No. Thereupon he (the Holy Prophet) said: If you did not observe fast, then you should observe fast for two days.  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ لَهُ أَوْ لآخَرَ أَصُمْتَ مِنْ سَرَرِ شَعْبَانَ قَالَ لاَ قَالَ فَإِذَا أَفْطَرْتَ فَصُمْ يَوْمَيْنِ  

Did you observe any fast in the middle of this month (Sha'ban)? He said: No. Thereupon the Messenger of Allah ﷺ said: Fast for two days instead of (one fast) when you have completed (fasts of) Ramadan.  

أَنَّ النَّبِيَّ ﷺ قَالَ لِرَجُلٍ هَلْ صُمْتَ مِنْ سُرَرِ هَذَا الشَّهْرِ شَيْئًا قَالَ لاَ فَقَالَ رَسُولُ اللَّهِ ﷺ فَإِذَا أَفْطَرْتَ مِنْ رَمَضَانَ فَصُمْ يَوْمَيْنِ مَكَانَهُ  

Did you observe fast in the middle of this month. i. e. Sha'ban? He said: No. Thereupon he said to him: When it is the end of Ramadan, then observe fast for one day or two (Shu'ba had some doubt about it) but he said: I think that he has said: two days.  

أَنَّ ﷺ قَالَ لِرَجُلٍ هَلْ صُمْتَ مِنْ سِرَرِ هَذَا الشَّهْرِ شَيْئًا يَعْنِي شَعْبَانَ قَالَ لاَ قَالَ فَقَالَ لَهُ إِذَا أَفْطَرْتَ رَمَضَانَ فَصُمْ يَوْمًا أَوْ يَوْمَيْنِ شُعْبَةُ الَّذِي شَكَّ فِيهِ قَالَ وَأَظُنُّهُ قَالَ يَوْمَيْنِ  

This hadith is narrated by 'Abdullah b. Hani b. Akhi Mutarrif with the same chain of transmitters.  

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ هَانِئِ ابْنِ أَخِي مُطَرِّفٍ فِي هَذَا الإِسْنَادِ بِمِثْلِهِ