What is the ruling on the imam being late for the agreed-upon time for establishing the prayer, under the pretext that it is a Sunnah, while this causes distress to the worshippers?

The Imam should be a role model for the worshipers, keen on performing the Sunnah prayers, and present before the prayer at an appropriate time to prepare for it. The Imam might be performing the Sunnah prayers at his home, but if the worshipers are inconvenienced by his delay, he should not insist on it; because affection and love between the Imam and the worshipers are Islamically required.