tamas tv ajnana-jam viddhi
mohanam sarva-dehinam
tan nibadhnati bharata

"O son of Bharata, know that the mode of darkness, born of ignorance, is the delusion of all embodied living entities. The results of this mode are madness, indolence and sleep, which bind the conditioned soul."

Bharata = offspring of Bharata dynasty [Arjuna]. The Lord tells Arjuna four points: what is tamo quality, why tamo quality is exhibited, what happens because of tamo quality and how tamo quality binds us in samsaram. So in this sloka we can see tamo quality, its cause, its operation and its effect. Tamas tu = while tamas quality [here the word tu differentiates tamas quality from satvam and rajas; one might manage satva and rajo qualities, but tamas quality is very dangerous], ajnana-jam = is off shoot of ignorance, viddhi = understand. Ignorance is misunderstanding and is opposite of Gyana, which is understanding a thing properly and truly. Agyana is not merely not understanding, but understanding in the wrong way! By understanding one as another is viparita gyana [விபரீத ஞானம்] or misunderstanding. This tamo quality emanates from ignorance or agyana. Sarva- dehinam = all bodies are, mohanam = in delusion [here mohanam does not mean faintness, but adopting practices and beliefs opposed to Dharma]. Gyana should be what is in accordance with Vedas. Here, Sri Krishna tells that tamas quality, will make the person to interpret wrongly Vedas and adopt wrong practices. Delusion is not accepting Vedas' orders or misinterpreting Vedas. From agyana or misunderstanding truth, is born tamas quality, which induces delusion and follow beliefs and practices opposed to Dharma. Pramada = carelessness, alasya = laziness, nidra = sleep, tan = these, nibhadnati = bind [in samsaram]. In our conversation, we appreciate a thing by telling 'pramadam'. But in Sanskrit, pramada means carelessness! Carelessness makes us to do all our duties wrongly. Vedas prescribe do's and don't's to various people at various times. They are rules and regulations. Carlessness would make us to do things wrongly and bind us in samsaram. Alasya is laziness. Some of us are to perform pooja early morning. If laziness is there, this is delayed and so we accumulate papa and get bonded in samsaram. Nidra is sleeping. Dharma shastra says that during sunrise, we should not be asleep. Our intellect or buddhi is bright in early mornings. But many follow late sleeping and skip early rise! Thus sleep prevents us from doing good things. We have to have sleep, which rests some organs. More sleep and no sleep are never good for us. There are many stages in sleep: jagrata or woken up stage, swapna or dreaming stage, sushupta or sleeping stage and turya or uniting with God and enjoying stage. In this last stage only we get the true rest and recharge for our organs. On some days we get up totally refreshed. If this is not there, then our sleep has been not proper. Mere duration of closing the eyes will not refresh and recharge our organs. Thus long sleep is an exhibition of tamas quality. We will not do what is to be done and vice versa, and do things at unscheduled time. Thus misunderstanding gives rise to tamo quality. Tamo quality would enable delusion and misinterpretation of Dharma. Delusion will result in carelessness, laziness and sleep. These will result in wrong actions and bind us in samsaram.