QUL

The Zani marries not but a Zaniyah or a Mushrikah; and the Zaniyah, none marries her except a Zani or a Mushrik. Such a thing is forbidden to the believers (3)

Here Allah tells us that the Zani (male who is guilty of illegal sex) does not have intercourse except with a Zaniyah (female who is guilty of illegal sex) or a Mushrikah (female idolator), meaning that no one would go along with him in this action except a sinful woman who is also guilty of Zina, or a Mushrikah who does not think it is unlawful. By the same token,

وَالزَّانِيَةُ لَا يَنكِحُهَا إِلَّا زَانٍ

(and the Zaniyah, none marries her except a Zani) a sinful man who is guilty of fornication,

 أَوْ مُشْرِكٌ

(or a Mushrik)(a man) who does not think it is unlawful.

وَحُرِّمَ ذَٰلِكَ عَلَى الْمُؤْمِنِينَ

(Such a thing is forbidden to the believers.) meaning, indulging in this, or marrying prostitutes, or marrying chaste women to immoral men. Qatadah and Muqatil bin Hayyan said: "Allah forbade the believers from marrying prostitutes." This Ayah is like the Ayah (about marrying slave-girls):

مُحْصَنَاتٍ غَيْرَ مُسَافِحَاتٍ وَلَا مُتَّخِذَاتِ أَخْدَانٍ

(they should be chaste, not committing illegal sex, nor taking boyfriends.)(4:25) And His saying:

مُحْصِنِينَ غَيْرَ مُسَافِحِينَ وَلَا مُتَّخِذِي أَخْدَانٍ

(desiring chastity not committing illegal sexual intercourse, nor taking them as girlfriends)(5:5).

Imam Ahmad recorded that 'Abdullah bin 'Amr, may Allah be pleased with him, said that a man among the believers asked the Messenger of Allah ﷺ for permission (to marry) a woman known as Umm Mahzul, who used to commit adultery, and who had stated the condition that she should spend on him. So he asked the Messenger of Allah ﷺ for permission, or he mentioned the matter to him. The Messenger of Allah ﷺ recited to him:

الزَّانِي لَا يَنكِحُ إِلَّا زَانِيَةً أَوْ مُشْرِكَةً وَالزَّانِيَةُ لَا يَنكِحُهَا إِلَّا زَانٍ أَوْ مُشْرِكٌ ۚ وَحُرِّمَ ذَٰلِكَ عَلَى الْمُؤْمِنِينَ

(The Zani marries not but a Zaniyah or a Mushrikah; and the Zaniyah, none marries her except Zani or a Mushrik. Such a thing is forbidden to the believers.)(24:3)

Ibn Abi Hatim recorded that Abu Hurayrah said,

لَا يَنْكِحُ الزَّانِي الْمَجْلُودُ إِلَّا مِثْلَهُ

(A Zani who has been flogged should not marry anyone except someone who is like him.) A similar report was recorded by Abu Dawud in his Sunan.