Glass's rifle was the one extravagance of his life, and when he rubbed grease into the spring mechanism of the hair trigger, he did so with the tender affection that other men might reserve for wife or child."
-- Narrator (chapter 2)

Importance: This sentence is suggesting that Glass has a very strong sentimental attachment to his rifle.

He saw the cubs before he saw the sow. There was a pair, and they tumbled toward him, bawling like playful dogs.
-- Narrator (chapter 3)

Importance: This is the first line that hints at the idea that the bear attack is coming. Since the reader likely knows ahead of time that there is a bear attack in this novel, this line tells us that the attack will happen soon. A few paragraphs after, Glass is attacked by the grizzly bear.

We need to make better time. I need two volunteers to stay with Glass. Stay with him here until he dies...
-- Captain Henry (chapter 4)