وَقَالَ مُحَمَّدٌ: سَمِعْتُ أَبَا إِسْحَاقَ إِبْرَاهِيمَ بْنَ عِيسَى الطَّالَقَانِيَّ، قَالَ: قُلْتُ لِعَبْدِ اللَّهِ بْنِ الْمُبَارَكِ: يَا أَبَا عَبْدِ الرَّحْمَنِ، الْحَدِيثُ الَّذِي جَاءَ: «إِنَّ مِنَ الْبِرِّ بَعْدَ الْبِرِّ أَنْ تُصَلِّيَ لِأَبَوَيْكَ مَعَ صَلَاتِكَ، وَتَصُومَ لَهُمَا مَعَ صَوْمِكَ». قَالَ: فَقَالَ عَبْدُ اللَّهِ: يَا أَبَا إِسْحَاقَ، عَمَّنْ هَذَا؟ قَالَ: قُلْتُ لَهُ: هَذَا مِنْ حَدِيثِ شِهَابِ بْنِ خِرَاشٍ. فَقَالَ: ثِقَةٌ، عَمَّنْ؟
Translation: Muḥammad said: “I heard Abū Isḥāq Ibrāhīm b. ʿĪsā al-Ṭālaqānī say: I asked ʿAbd Allāh b. al-Mubārak, ‘O Abū ʿAbd al-Raḥmān, what of the report that has reached us: “Part of dutifulness after dutifulness is to pray on behalf of your parents alongside your own prayer, and to fast on their behalf alongside your own fast”?’ ʿAbd Allāh replied, ‘O Abū Isḥāq, from whom is this?’ I said, ‘It is from the narration of Shihāb b. Khirāsh.’ He replied, ‘He is trustworthy; from whom [did he receive it]?’”
The point is verifying attribution, not approving a report because its content sounds virtuous. Ibn al-Mubārak recognized one named transmitter as reliable while continuing to demand the next link.