It is reported that once a heretic was brought to Harun al-Rashid (the ‘Abbasi Khalif) who subsequently ordered his execution.

The heretic said to him, ‘Why are you executing me?’

He said, ‘To relieve the worshippers of you (and your heresy).’

The heretic said, ‘And what can you do about the one thousand narrations that I attributed to the Messenger of Allah (sallallahu `alayhi wa sallam) although he did not utter a single letter of them?’

Al-Rashid then said to him,

‘O enemy of Allah! And what can do you about Abu Ishaq al-Fazari and Ibn al-Mubarak who will sift through them and extract them one by one!’

Source: Tadhkirat al-Huffadh by Imam al-Dhahabi.