The Prophet (peace be upon him) pointed three times towards his chest and said, "Taqwa (piety) is here".[Muslim]
One might be deceived by searching for taqwa of a person by looking at the way he dresses, or in his countenance and shape, or in his external appearance. But the true centre and source of taqwa is within his chest - in his qalb. The Prophet has drawn our attention with emphasis towards this key point by pointing towards his chest three times.
The Quran has repeatedly called attention towards the fact that real accountability will be of deeds that are based on qalb. If a man were to forcibly commit kufr (deny the existence of Allah) by his tongue, and yet his qalb affirms iman (faith in Allah), then he will not be questioned on the Day of Judgment for his denial under duress. His qalb is satisfied on the basis of iman. Pointing towards the chest, he stated that you may commit sin, but you will be questioned about that sin which your qalb intended, and what the qalb has earned. Man is responsible for what his qalb intended, and what it gained in return for his deeds. Truly man is entirely accountable for what his qalb earns.
Man is answerable because Allah has given him freedom of choice. A person may do good deeds or evil deeds as per his wishes. Since the intention is controlled by the qalb, the real responsibility lies with the qalb. The qalb is responsible for committing sin. In other words, it is that inner self which controls emotions, intentions, and motives. On the Day of Judgment, only that person will attain salvation and enter into the presence of Allah who has a sound qalb.
"A Righteous Heart: The Axis of One's Deeds" - Khurram Murad