The Blessed Lord said The sages understand Sannyasa to be the renunciation of action with desire; the wise declare the abandonment of the fruits of all actions as Tyaga.
In simple words
Krishna answers: "The wise say that giving up all desire-driven action is renunciation. And giving up attachment to the results of all actions — that is what is called surrender."
English Commentary By Swami Sivananda18.2 काम्यानाम् (of) desireful? कर्मणाम् of actions? न्यासम् the renunciation? संन्यासम् Sannyasa? कवयः the sages? विदुः understand? सर्वकर्मफलत्यागम् the abandonment of the fruits of all works? प्राहुः declare? त्यागम् abandonment? विचक्षणाः the wise.Commentary Kamya Karmani Activities such as the Asvamedha (a special sacrifice)? etc.? which are performed for the attainment of specific selfish ends. The wise men declare that Tyaga means abandonment of the fruits of all the Nitya and Naimittika works (ordinary and extraordinary or occasional duties).The rootmeaning of the words Sannyasa and Tyaga is to give up. In popular usage Sannyasa and Tyaga are more or less synonymous. Both mean renunciation. The two words do not mean two altogether distinct ideas as stone and fruit? or pot and cloth. They convey the same general idea with a slight distinction.An objector asks It is said that the Nitya and Naimittika actions cannot produce any fruits. Why then is the relinishment of their fruits mentioned here It is like asking for the relinishment of the barren womans sonWe say The objection is not correct. In the opinion of the Lord? ordinary and occasional duties cause their own fruits (vide XVIII.12). Sannyasins alone who have renounced the desire for the fruits of actions will not get the fruits? but other persons will have to reap the fruits of the ordinary and occasional actions.If one renounces all actions after the attainment of Selfrealisation and enters into the fourth order of life (Sannyasa) it is called VidvatSannyasa. If one renounces all actions and enters into the order of Sannyasa for the sake of doing VedantaVichara (or reflection on the truths of the Vedantaphilosophy and on the true significance of the great sentences of the Upanishads which reveal the identity of the individual soul with the Supreme Being) and for thus attaining Selfrealisation? it is called VividishaSannyasa.
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# BG 18.2 — Commentary Translation
The renunciation of desire-driven actions is called sannyasa, and the relinquishment of attachment to the fruits of all actions is called tyaga. To those unversed in the teachings of scripture, there appears to be no distinction between these two—for desire always seeks the attainment of fruits. Thus, the abandonment of desire-impelled actions and the renunciation of attachment to the results of action seem identical. This confusion arises only from ignorance of the scriptures or superficial study of them.
There is no doubt that both ultimately mean the renunciation of desire. Yet there exists a subtle difference between tyaga and sannyasa. Nevertheless, tyaga is an inseparable component of sannyasa. A person acts in the present and hopes to receive the desired fruit in the future. The result of present action manifests as future fruit. Therefore, actionless action can occur only in the present, whereas the mental agitation born of concern for future enjoyment belongs to the future. The completion of present action culminates in future fruit. Desire and distraction create inner turbulence. The more intense the desire, the greater the depletion of our inner energies, and such an enfeebled person cannot perform any action with skill and enthusiasm. It is also noteworthy that it is the ego, or the individual self, that desires. Thus, the dissolution of ego means the withdrawal of the individual self and the seeker's firm establishment in their highest nature.
Actions occur in the present, and their fruits may be obtained in the future. One who concerns oneself with results loses the capacity to act effectively in the present. Naturally, the likelihood of obtaining the desired fruit diminishes, for the fruit of action depends upon the effort of the doer and many other factors governed by the laws of nature. Therefore, we are taught to renounce attachment to fruits.
In brief, tyaga is the means, and sannyasa is the goal. The practice of tyaga and sannyasa relates to our actions. Lord Sri Krishna never tires of emphasizing the importance of action. Neither of these terms suggests that we should neglect our duties. On the contrary, both insist upon the performance of action. We must act. Yet these actions must be free from ego, selfishness, and attachment to results. It is attachment to fruits that obstructs our effectiveness in action. In the absence of such attachment, our actions can bestow upon us their full reward. We may say that the definitions given in the Gita for these two terms are more liberal and tolerant than the meanings attributed to them in the Vedas.
Regarding whether the ignorant person should perform action or not...