Translation:

18. The (people) said: "for us We augur an evil omen from you: if ye desist not we will certainly stone you and a grievous punishment indeed will be inflicted on you by us."

Notes (Tafseer)

3963. Tair means a bird. Like the Roman augurs, the Arabs had a superstition about deriving omens from birds. Cf. the English word "auspicious", from the Latin avis, a bird, and specio, I see. From Tair (bird) came ta-taiyara, or ittaiyara, to draw evil omens. Because the prophets of Allah denounced evil, the evil-doers thought that they brought ill-luck to them. As a matter of fact any evil that happened to them was the result of their own ill-deeds. Cf. vii. 131, where the Egyptians ascribed their calamities to the ill-luck brought by Moses: and xxvii. 47, where the Thamud ascribed ill-luck to the preaching of Salih.