Going to the mosque when fasting

Abul-Mutawakkil Al-Nâjî reports:

When Abû Hurayrah and his companions fasted, they would sit in the mosque and say, “let us purify our fast.”

Hunâd b. Al-Sarî, Kitâb Al-Zuhd, article 1207

More:

1. Eating to Fast [not Fasting to Eat]
2. Make Fasting Different
3. Sinning while fasting [does it break the fast?]
4. Breaking the fast as soon as the sun sets [Sunnah of Fasting]
5. Umar’s Instructions on the First Night of Ramadan
6. Do you have to make up fasts consecutively? [Fiqh of Fasting]
7. Training Children for Worship