Rashi, Dunash: My heart told me, she wore out and aged due to adultery. Now that she is old, her Zenus will depart from her and she will retract. Behold, she is Mezanah like initially! Yiznu is an expression of leaving. The Targum of Zonah is always Nafkas Bara (she goes outside). Also Yonason translates like this. It is as if it says la'Balah b'Ni'ufim. Often the prefix Beis is omitted, e.g. "va'Teshev Beis Aviha" (Bereishis 38:11).

Rashi citing Menachem: "La'Balah" is like "Tevel Asu ¹ " (Vayikra 20:12).

Radak: Hashem said, when I saw her ways, I said 'will an old Zonah do adultery?!' Balah is old, like "Acharei Belosi" (Bereishis 18:12). This is a Mashal. She became old with [serving] idolatry many years, and she still did not put to her heart to return to Me!

Malbim: I, the husband, when I saw this, I said that this adultery will wear out the adulterers; they will rot. La'Balah is the illness and Tzara'as that clings to those who are Mezanah. It wears out the entire body and their limbs. I cursed them, that the Balah that clings to adulterers should cling to them.

Radak: Now the idolatry, her harlotry, will perish, and she with it. In her Galus, all the idols and those who serve them will be eradicated. Yiznu is leaving their Reshus and land, for a Zonah leaves her husband's Reshus. The same applies to "va'Tiznah Alav Pilagsho" (Shoftim 19:2). Yiznu is written with a Hei, but pronounced with a Vov, like "Yadeinu Lo Shafchu" (Devarim 21:7).

Malbim: I said that both the adulterers and she will rot.