What is the ruling on performing tarawih prayers very quickly, finishing in under eight minutes?

Summary

This ruling stresses that tamakninah (tranquility in each movement) is a pillar of prayer alongside the pillars of action, based on the hadith of the man told to repeat his prayer for lacking it. Bowing must be accompanied by tamakninah, and merely bending down and rising straight away is not sufficient. A hurried prayer can hardly achieve khushu', so prayer should be performed calmly, as the Prophet's night prayer was complete in its bowing, prostration and standing.

Written in our own words from the original fatwa — check the source before acting on it.