What are examples of when Jim's loyalty is shown in the book? quotations too?
Jim's loyalty is signalled by his high regard for Huck. According to Huck, he calls him "honey" and he "pets" him all the time by not waking Huck up when it is his turn to watch the raft.
Besides, Jim proves his faithfulness to Huck by always patiently waiting for Huck's return and looking after the raft, when he could just have left.
Another instance of Jim's loyalty is shown when he comes out of the woods to help the doctor to take the bullet out of Tom's leg, at the risk of being re-captured.
But somehow I couldn't seem to strike no places to harden me against him, but only the other kind. I'd see him standing my watch on top of his 'n, 'stead of calling me, so I could go on sleeping; and see him how glad he was when I come back out of the fog; (…) and would always call me honey, and pet me and do everything he could think of for me, and how good he always was; and at last I struck the time I saved him by telling the men we had small-pox aboard, and he was so grateful, and said I was the best friend old Jim ever had in the world, and the only one he's got now; (…). (AOHF, 284)
Don't be no rougher on him than you're obleeged to, because he ain't a bad nigger. When I got to where I found the boy I see I couldn't cut the bullet out without some help, and he warn't in no condition for me to leave to go and get help; and he got a little worse and a little worse, and after a long time he went out of his head, and wouldn't let me come a-nigh him any more, and said if I chalked his raft he'd kill me, and no end of wild foolishness like that, and I see I couldn't do anything at all with him; so I says, I got to have help somehow; and the minute I says it out crawls this nigger from somewheres and says he'll help, and he done it, too, and done it very well. (AOHF, 377)