Valmiki Ramayana Ayodhya Kanda Sarga 109 Shloka 21

मनसा by mind, सम्प्रधार्य having conceived, कायेन by the body, पापम् sin (evil deed), कुरुते is committed, जिह्वया with tongue, अनृतं च falsehood, आह is spoken, पातकं कर्म sinful action, त्रिविधम् is in these three ways.

At first a man conceives an evil idea in his mind, then executes it through evil deed with his body and tells a lie through his tongue. Thus sinful action is three dimensional (mental, physical and vocal).