Commentaire sur Rois 2 7:3

There were four men. Geichazi and his sons.¹See Maseches Sanhedrin 107b. ²These four were the only people suffering from tzora’as. Elisha had healed all other Bnei Yisroel suffering from tzora’as.—Malbim

The questions: Why does it say people who are metzoraim were outside the gate?

At the entrance of the gate. As it is stated, “He shall live alone; outside the camp shall be his habitation.”³Vayikra 13:46. This is proscribed by the Torah for people who suffer from tzora’as.

Four men: Our sages, may their memory be for a blessing, explained that these were Gehazi and his three sons, for Elisha cured other metzoraim, as we saw with regard to Na'aman, and as we saw in the words of the young woman who said to Na'aman's wife that Elisha would cure him. Certainly, she said this (only) because curing people was (Elisha's) practice. It is explained that this was Gehazi and his sons, who could not be cured. Thus it is said

They were metzoraim: That they remained metzoraim and were not cured. Since they were afflicted in Shomron, they sent them beyond the city wall, as is the law of metzora: send him out from walled cities, as it is written in the first chapter of the tractate Kelim.