Sincere Words Penetrate & Illuminate Sincere Hearts
Whatever [sincerely] emerges from the heart, enters the heart. But whatever is limited to the tongue, does not go beyond the ears. Then, on penetrating the heart, it may either encounter an opposition which repels it with total rejection, as in the case of unbelievers; or an unwillingness, as with hypocrites; or a thin veil, as with sinners; or it may touch its essence and reality such that it gives rise to courage and restraint for acts [of worship], as in the case of truthful seekers [of Allah].
Ahmad Zarruq, Qawa‘id al-Tasawwuf – Taken from here