" And every evening, when Frith has done his day's work and lies calm and easy in the red sky, El-ahrairah and his children and his children's children come out of their holes and feed and play in his sight, for they are his friends and he has promised them that they can never be destroyed."
Also the bit where Bigwig is fighting Woundwort and tells him that he will defend that run until he's dead. And this from the rabbit who, in the beginning, was objecting to Hazel's leadership.
Bigwig: My Chief Rabbit has told me to defend this run and until he says otherwise I shall stay here.
"Oh fly away, great bird so white...you know, he made me feel I could fly, too." And so Kehaar leaves, if only for now.
From the beginning, Hazel is concerned that Bigwig might try to "take over" and run things, and he does occasionally get a bit blustery—but in fact, reading the novel, Bigwig has very little ambition and never really makes any move to countermand or undermine Hazel. His sole issue is that he refuses to call him Chief or give him the -rah suffix; but at worst, he consistently acts as if he believes he and Hazel are co-captains of the group, with Hazel being the "people person" and himself the world-wise combat veteran with survival knowledge. He asks Hazel's opinion, takes pointed suggestions and even orders from him without complaint, and consistently acts in tandem with him. At worst, it can't be said Bigwig acts as if he himself is or ought to be Chief; he simply has a little bit of pride and ego wrapped up in willingly subordinating himself to Hazel, but always treats him as an equal.
Even back in Sandleford, before the journey ever began, Bigwig didn't give orders to Hazel and willingly accepted that he was joining the group rather than taking command of it, and that it was Hazel's group. He even phrases his first criticism as "If you'll take my advice..."
At the Warren of the Shining Wires, when Fiver tries to leave and Hazel offers to go with him for a while even though it's dangerous, Bigwig blows up at what he views as Fiver's nonsense going too far because it's placing Hazel's life in danger now. Specifically, he aims his fury at Fiver's nebulous feelings risking the life of "one of the best rabbits we've got."
In short, from the very first terrible night in the woods, Bigwig functions instinctively as Hazel's perfect captain of Owsla, even before they learn to like and understand one another.
Best of all, after the group makes it to the Down, Hazel rewards Bigwig's trust in him, as well as the trust of the others, recognizing that his planning alone couldn't replace Bigwig's experience and courage, Fiver's insight or Blackberry's intelligence etc. The new warren is eventually run by a 'free and easy' Owsla. All contributions made by rabbits are given equal respect and there doesn't appear to be anything in the way of oppressive hierarchy such as at Efrafa or even Sandleford, where bigger rabbits get the choicest food and mates and bully the weaker rabbits. Every rabbit of the Down is an equal member entitled to the same privileges as anyone else.
When Strawberry joins the band of travelers. Silver sneers at him that they don't like rabbits who betray them, and he'd "Better go back to Nildro-Hain", his mate. Strawberry gives a cry of pain, and finally manages to whimper two words: "The wires." Having seen firsthand how much Nildro-Hain meant to Strawberry, the news that she has died—so suddenly and unnecessarily—is like a knife in the heart of all readers. The fact that his mate's death hurt him so badly that even someone like Strawberry, so jaded to constant death that he completely shrugged off the loss of his close friend Kingcup, couldn't bear to live without her made this troper tear up. Badly. The heartwarming part is Hazel's immediate response.
"Don't say any more. You can come with us. Poor fellow."
Pipkin's simple Catchphrase: "I'll come with you, Hazel-rah."
Also for Pipkin: In the final battle, he begs to be allowed to risk his own life remaining in the Honeycomb to try to wake Fiver, rather than burying himself in a burrow with the others. Hazel has to order him not to do it.
Bluebell caring for his captain, and telling the frightened does a story during the fight, to keep them from panicking.
"Oh, Frith on the hills! He must have made it just for us!"
"Frith may have made it... but Fiver found it."
Bigwig and Hyzenthlay's interactions in Efrafa are ridiculously cute. Just the way they reassure each other and keep each other going...
"I would rather be here, now, as we are, than to never have left Efrafa."
Hazel's mouse, returning to warn him about the Efrafans. Even though he didn't realize what was going on, he saved their lives. After Bigwig shrugging off the idea of rescuing the mouse in the first place, it's great to see how useful their little friend really was.
Fiver taking care of Hazel while the latter was recovering from being shot in the leg.
When Kehaar finds out Hazel has been shot, he expresses concern and asks if Fiver has removed the 'black stones' (shot) to help Hazel recover. Then when Kehaar sees Hazel, he begins to diligently pluck the shot from Hazel's leg with his beak.
Through the latter half of the novel, Hazel, never very patient with Bluebell, had a habit of finishing his limericks in Sarcasm Mode. However, some months after the battle with Efrafa, he meets Bluebell leading a winter shelter digging crew:
Bluebell:Ah ha, ah ha, O Hazel-rah! The burrow's snug, it hath been dug, 'tis free from beetle, worm and slug. And in the snow, when down we go—
Hazel: Then what a lot to you we'll owe.
Towards the end of Watership Down (the novel), months after their adventures, Hazel happens upon a mother rabbit telling her kits a story ostensibly starring the rabbit's legendary hero El-ahrairah. It gradually dawns on him that the tale is really his story: the tale of the escape of his True Companions from Sandleford and journey to Watership Down. Many Tears of Joy ensue.
At the end, when an old and weary Hazel suddenly starts feeling better than he ever had in his whole life... then turns and sees his own dead body lying in the grass. He feels just a fleeting moment of regret, then happily bounds off to join all those who've gone before.
In the film, Hazel's prayer to Frith: "Lord Frith, I know you've looked after us well, and it's wrong to ask even more of you. But my people are in terrible danger, and so I would like to make a bargain with you. My life in return for theirs."
Adding to that, Frith's reply, highlighting the fact that these rabbits are not the only ones who can be heroes, and that people like them live and die every day.
"Not a day goes by but a doe offers her life for her kittens, or some honest captain of Owsla his life for his Chief Rabbit. Sometimes the bargain is accepted; sometimes it is not. But there is no bargain here—for what is, is what must be."
That bears thinking about as well, and crosses over with a CMOA. Frith, the all-powerful god, is essentially saying that in this, Hazel creates his own fate. Neither Frith nor the Black Rabbit interferes. Which means that the miracle they pull off? That was them. No god made that happen. It was their strength, their courage, and their spirits and ingenuity alone that saved Watership. Hazel-rah, indeed.
Is it a mystery why he was asked to join Frith's Owsla?
Not Frith's Owsla - El-ahrairah's. Which is arguably even better. Also, that line about bargains? In the book, the Black Rabbit says that to El-ahrairah. Hazel is in exceptional company there.
When El-Ahrairah (or the Black Rabbit, in the movie) comes to claim Hazel, he turns out to be very polite and friendly, reassuring Hazel that the warren will continue to thrive. His calling is more like an invitation to go on a new adventure, and Hazel is happy to enter the next life.