If the imam does not deliver the khutbah on Friday, how many rak'ahs should he pray?

Ayyub narrates that once the governor of Bahrain fell ill. He ordered a man, and that man led the people in the Friday prayer. He did not deliver a sermon and performed four units of prayer. When Muhammad learned of this, he said that he acted according to the Sunnah.

The same is also narrated from Hazrat Ibn Sirin.

Ibrahim says that if the imam does not deliver the sermon on Friday, he should lead four units (rak‘ahs) of prayer.

Hasan says that if the Imam does not deliver the sermon on Friday, he should lead four units (rak‘ahs) of prayer.

Hazrat Tawus says that if the Imam delivers the sermon on Friday, he should lead two rak‘ahs (units of prayer), and if he does not deliver the sermon, he should lead four rak‘ahs of prayer.

Hazrat Zuhri used to lead four rak‘ahs in case the sermon was not delivered.

Hazrat Dahhak used to lead four rak‘ahs in prayer when the sermon was not delivered.

Hazrat Burd says that Hazrat Mak'hool set out with the intention of Hajj. When he reached the place of Tabuk, Friday arrived. Their Imam led two units (rak‘at) of prayer and did not deliver the sermon (khutbah). Hazrat Mak'hool said: May Allah strike him! He shortened the people's prayer and did not deliver the sermon either. The Friday prayer is shortened because of the sermon.