Is performing Ramal (rapid walking) in the valley during Sa'i obligatory?

Primary text

Performing Ramal in the valley between the landmarks is an emphasized Sunnah (mustaḥabba), as the Prophet, peace be upon him, and his Companions performed it. However, it is not obligatory, and its omission incurs no penalty. Ibn Umar stated that he saw the Prophet performing it, and he also saw him walking when he himself was an old man. This is analogized to the omission of Ramal during the Tawaf of the Ka'bah, for which there is no penalty.