Episode scene:

These trademark words of Owen Wister’s hero are spoken by the Virginian at the end of the episode, in response to Trampas’ suggestion that his friend would make a good bank robber.

Quotation from the book (Chapter 2):

It was now the Virginian’s turn to bet, or leave the game, and he did not speak at once.

Therefore, Trampas spoke. “Your bet, you son-of-a-_____.”

The Virginian’s pistol came out, and his hand lay on the table, holding it aimed. And with a voice as gentle as ever, the voice that sounded almost like a caress, but drawling a very little more than usual, so that there was almost a space between each word, he issued his orders to the man Trampas: -

“When you call me that, smile!” And he looked at Trampas across the table.

Additional comments:

1. The TV series’ creators decided to make Trampas and the Virginian best friends, although their friendship does get off to a rocky start (see Ride a Dark Trail.) In the book, however, they are deadly enemies from the moment they meet in that card game, and remain so to the end.
2. In Ride a Dark Trail, Steve applies the epithet son-of-a______ to Trampas during a card game.
3. In If You Have Tears the Virginian puts his pistol on the table during a card game in which the dealer has been cheating.