The meaning of the verses is that Allah sent two messengers to the village, and the people denied them. Allah then strengthened the two with a third, and together they said, "Indeed, we are messengers to you" (36:14).
The people answered with three objections: you are only human like us, the Most Merciful has not sent down anything, and you are lying (36:15). The messengers replied calmly that their Lord knows they are truly His messengers, and that their duty is only to deliver the message clearly (36:16-17).
The people then said they saw a bad omen in the messengers, and threatened to stone them and to harm them with a painful punishment if they did not stop (36:18). The messengers answered that the omen was in the people themselves, because they had been reminded and refused. They were, in the words of the verse, a people who transgress (36:19).
- First, denial: they refused the message and called the messengers liars.
- Then, blaming the messengers for their own troubles by calling them a bad omen.
- Finally, threats of stoning and punishment.