sri-bhagavan uvaca
kalo ’smi loka-ksaya-krt pravrddho
lokan samahartum iha pravrttah
rte ’pi tvam na bhavisyanti sarve
ye ’vasthitah pratyanikesu yodhah

"The Supreme Personality of Godhead said: Time I am, the great destroyer of the worlds, and I have come here to destroy all people. With the exception of you [the Pandavas], all the soldiers here on both sides will be slain."

Kalo'smi = [I, Sri Krishna] am god of Time. This answers Arjuna's question 'ko bhavan?' But we have to be careful in understanding this. Arjuna's question was not because he did not know who Sri Krishna was. It is also not correct to understand that Sri Krishna is the god of Time as the direct reply. Arjuna's question was to know for what purpose the Lord had assumed Viswaroopam. And, Sri Krishna's reply that He was the god of Time means, He was marking the time of end of all in the opposite camp, such as Bhishma, Drona and the Kauravas. That is He is the Destiny to determine the life of all these people. Loka = World or Universe, that is all wicked persons in this World or Universe, those who were harming the Earth, ksaya-krt = destroying action or destruction, pravrddha = grown well, that is assuming this gigantic Viswaroopam. To destroy all these wicked persons harming the World, the Lord had taken the Viswaroopam and determing their destiny. The Lord is the Destiny, determining everyones birth and death. Lokan = all Worlds, that is the wicked persons in all worlds, samahartum = completely destroying, iha = here, in this battlefield of Kurukshetra, in the sight of Arjuna, pravrtta = has been started. [Note the difference in pravrddha and pravrtta]. As a Single Person, the Lord is appearing to destroy all the evil persons in all the worlds. Sarve = all thses persons standing to fight with Arjuna, ye = those, yodha = warriors, pratyanikesu = opposing Arjuna, na bhavisyanti = will not exist, rte pi = even without, tvam = you [Arjuna]. That is even if Arjuna was not there or he did not fight, all these wicked persons standing in the battlefield opposing Pandavas are going to be finished by the Lord. That is certain. If Arjuna fought, he could gain some reputation; otherwise also they are going to be destroyed. When the Lord says He is the god of Time [Kala], three interpretations are possible. One could be that the Lord is the inner Prime mover of the Time, like days, hours, etc. Another meaning is that Kala refers to the measurement of time or period. That is counting the period upto which these persons would live. According to shastras, Three gods are associated with death - Mruthyu , Kala and Dharma. Dharma god decides on the result of everyones fate according to theier actions of papa/ punya. Kala god decides on the period upto which anyone could live. Mruthyu god relieves soul from the body. By sayig Kalosmi, the Lord is telling that He is the antaryami for all these three gods. Better, He is the One deciding on their destiny. He has assumed this mammoth form to destroy the world. Here we should remember that because Arjuna requested the Lord, He assumed this Viswaroopam and not to destroy immediately. We have to remember Arjuna wanted to know the purpose of Viswaroopam. In interpreting slokas, we have to remember the earlier slokas. Then only, a convincing meaning could be found. Our great commentators followed this principle only. Interpreting a sloka in isolation would lead to contradiction with upcoming or earlier slokas. Present Viswaroopam was the result of Arjuna's prayer, and it was merely to show; but Viswaroopam as such has to have a purpose and that is what Arjuna desired to know. The Lord thus tells Arjuna that He is going to decide the destiny of all these persons. To destroy all the wicked persons in all the Worlds, Single-handedly, the Lord has taken this gigantic form, Viswaroopam. He does not need Yudhishtra nor Bhima nor Arjuna to destroy them. He alone is going to destroy them. Arjuna is only a tool and if he fought he could gain some name; even without that, their destinies were all finalised and the Lord had initiated action. Arjuna should never think that if he did not fight or if he were not there, these persons standing to oppose Arjuna, would not perish. Sarve na bhavisyanti - all of them will not exist, anyway. The Lord has already marked their time. Alwar praises the Lord as having the discus of time [காலச் சக்கரம்]. The movement of the discus decides the future of all. The Lord conveys the message that He is the One deciding on the destiny of all - their creations, their destructions and their sustenance. His sankalpa or will power alone would prevail, irrespective of Arjuna's actions.