Which is better: voluntary fasting, or glorifying, exalting, and magnifying Allah?

Voluntary fasting and remembrance (dhikr) are both acts of worship with immense reward. However, the prophetic narrations (hadith) have consistently emphasized the virtue of remembrance, such as the Prophet, peace and blessings be upon him, saying: "To say 'Subhan Allah, walhamdulillah, wa la ilaha illa Allah, wallahu akbar' (Glory be to Allah, and praise be to Allah, and there is no god but Allah, and Allah is the Greatest) is dearer to me than all that the sun rises upon." And he, peace and blessings be upon him, said: "Your tongue should remain moist with the remembrance of Allah." He also said: "Shall I not inform you of the best of your deeds, the purest in the sight of your King, the highest in your ranks, better for you than spending gold and silver, and better for you than meeting your enemy and striking their necks and them striking your necks?" They said: "Yes, indeed." He said: "The remembrance of Allah."

As for voluntary fasting, it also carries great reward, such as his saying, peace and blessings be upon him: "Whoever fasts a day for the sake of Allah, Allah will distance his face from the Hellfire by seventy autumns."

A Muslim can combine both acts of obedience, so he may fast voluntarily and increase his remembrance of Allah Almighty, and this is the most preferable.