The word qalb, which is used for ‘heart’ in Arabic, has two meanings. Firstly, there is the apparent and physical meaning, and then there is the spiritual meaning. The apparent meaning of qalb is one of ‘turning about’. Since it is the heart that causes the circulation of blood in our bodies, it is referred to as qalb in Arabic.
In the spiritual sense, this word implies that any progress an individual hopes to attain in terms of spirituality can only be attained through the power of the heart. Just as the circulation of blood, which is absolutely critical in sustaining human life, is powered by the heart or qalb, in the same manner, all forms of spiritual advancement are dependent on the power of the heart.
Hazrat Mirza Ghulam Ahmad (as), Malfuzat – Volume II (Farnham, Surrey: Islam International Publications Ltd., 2019), 119.