The importance of silent dhikr

The author of Fiqh al-sunna writes:

The purpose of dhikr is to purify hearts and souls and awaken the human conscience. The Qur'an says:

"And establish regular prayer, for prayer restrains from shameful and unjust deeds, and remembrance of Allah is the greatest thing in life, without doubt." (29:45)

In other words, the remembrance of Allah has a greater impact in restraining one from shameful and unjust deeds than just the formal regular prayer. This is so because when a servant opens up his soul to his Lord, extolling His praise, Allah strengthens him with His light, increasing thereby his faith and conviction, and reassuring his mind and heart. This refers to:

"those who believe, and whose hearts find satisfaction in the remembrance of Allah, for without doubt in the remembrance of Allah do hearts find satisfaction." (13:28)

And when hearts are satisfied with the Truth, they turn to the highest ideals without being deflected by impulses of desire or lust. This underscores the importance of dhikr in man's life. Obviously it would be unreasonable to expect these results just by uttering certain words, for words of the tongue unsupported by a willing heart are of no consequence.