ततः श्वेतैर्हयैर्युक्ते महति स्यन्दने स्थितौ।माधवः पाण्डवश्चैव दिव्यौ शङ्खौ प्रदध्मतुः॥
tataḥ śvetairhayairyukte mahati syandane sthitaumādhavaḥ pāṇḍavaścaiva divyau śaṅkhau pradadhmatuḥ
Word by word
The verse says
Then, standing in their great chariot yoked with white horses, Krishna and Arjuna blew their divine conches.
In plain words
The other side answers. Two men in one chariot, and the horses are white.
This is the first time in the Gita that Krishna and Arjuna appear together, and the poem puts them in a single vehicle from the start. One holds the reins. The other holds the bow.
They will not leave that chariot for eighteen chapters.
Where you've felt this · in friendship
You and your father drive eight hours through the night. He steers, you read the road signs. Somewhere after midnight he tells you something about his own father that he has never said across a table. Facing the same way turned out to be easier than facing each other.
Going deeper
The whole Gita happens in this chariot, and the arrangement is not decorative.
Krishna is the driver. That is a servant's job, and he took it deliberately - when both sides came asking for his help, he offered a choice between his armies and himself unarmed, and Arjuna chose him. So God is here holding the reins for a friend, having refused to pick up a weapon.
The image became a standard one in later Indian thought: the body as chariot, the senses as horses, the mind as reins, and the self as the passenger who ought to be in charge. The Upanishads use it directly. Here it is not a metaphor yet. It is simply two friends in a vehicle.
That is worth holding on to. Before the Gita is philosophy, it is a conversation between people who know each other well, at the worst possible moment, in a cramped space with nowhere to walk away to.