Is ensuring water reaches the spaces between the toes mandatory during Wudu?
Chapter on Siwak and the Sunnah of Wudu
Al-Mughni
Book of Purification
Primary text
It is recommended to perform 'Takhleel' (interlacing water) between the toes of the feet. This recommendation is strongly supported by the saying of the Prophet, peace be upon him, to Laqit ibn Saburah: 'Complete your ablution and perform Takhleel of the fingers.' Furthermore, it is narrated that the Prophet, peace be upon him, used his pinky finger to interlace between the toes of his feet. One should begin interlacing the right foot from its smallest toe towards the big toe, and the left foot from its big toe towards the smallest toe, following the Prophet's preference for starting with the right side (Taymun) in all affairs.
Supporting text
If a person submerges the foot in water and moves it, Imam Ahmad expressed hope that this suffices for Takhleel, especially if water might slip off the limb in winter. If the toes are touching but connected, it is not obligatory to separate them as they are considered like a single digit. If they are not touching, water must reach the space between them.