How does Mr. Campbell feel about David? What tells us this?

Mr. Campbell cares deeply for David and gives him gifts from he and his wife. We know he care for the boy because he gets all choked up and has difficulty speaking.

"Why, very well said," replied Mr. Campbell, heartily. "And now to come to the material, or (to make a quibble) to the immaterial. I have here a little packet which contains four things." He tugged it, as he spoke, and with some great difficulty, from the skirt pocket of his coat. "Of these four things, the first is your legal due: the little pickle money for your father's books and plenishing, which I have bought (as I have explained from the first) in the design of re-selling at a profit to the incoming dominie. The other three are gifties that Mrs. Campbell and myself would be blithe of your acceptance. The first, which is round, will likely please ye best at the first off-go; but, O Davie, laddie, it's but a drop of water in the sea; it'll help you but a step, and vanish like the morning. The second, which is flat and square and written upon, will stand by you through life, like a good staff for the road, and a good pillow to your head in sickness. And as for the last, which is cubical, that'll see you, it's my prayerful wish, into a better land."