How we cite our quotes:
On that day of the week and at that time of day people of one set, all acquainted with one another, used to meet on the ice. There were crack skaters there, showing off their skill, and learners clinging to chairs with timid, awkward movements, boys, and elderly people skating with hygienic motives. They seemed to Levin an elect band of blissful beings because they were here, near her. All the skaters, it seemed, with perfect self-possession, skated towards her, skated by her, even spoke to her, and were happy, quite apart from her, enjoying the capital ice and the fine weather. (1.9.5)
Such is the depth of Levin's infatuation that he is jealous of the people who are skating on the ice at the same time as Kitty.
Alexey Alexandrovitch was not jealous. Jealousy according to his notions was an insult to one's wife, and one ought to have confidence in one's wife. Why one ought to have confidence – that is to say, complete conviction that his young wife would always love him – he did not ask himself. But he had no experience of lack of confidence, because he had confidence in her, and told himself that he ought to have it. Now, though his conviction that jealousy was a shameful feeling and that one ought to feel confidence, had not broken down, he felt that he was standing face to face with something illogical and irrational, and did not know what was to be done. Alexey Alexandrovitch was standing face to face with life, with the possibility of his wife's loving someone other than himself, and this seemed to him very irrational and incomprehensible because it was life itself. (2.8.4)
It does not occur to Karenin to be jealous because he cannot stand the idea of his wife loving another man. Instead, he views his relations with his wife in the coldest, most rational way possible.
But he could not at once recall what he had been going to say. These fits of jealousy, which of late had been more and more frequent with her, horrified him, and however much he tried to disguise the fact, made him feel cold to her, although he knew the cause of her jealousy was her love for him. (4.3.17)
Anna's constant jealousy begins to severely alienate Vronsky.