Ibn Kathir said:
“Here Allah forbids the believers to marry a mushrik woman who worships idols, and if this were general in meaning, it would include every mushrik woman, whether she is of the people of the Book or is an idol worshipper, but the women of the people of the Book are excluded from that in the verse (interpretation of the meaning):
{(Lawful to you in marriage) are chaste women from the believers and chaste women from those who were given the Scripture (Jews and Christians) before your time when you have given their due Mahr (bridal-money given by the husband to his wife at the time of marriage), desiring chastity (i.e. taking them in legal wedlock) not committing illegal sexual intercourse, nor taking them as girlfriends} [Al-Ma'idah 5:5]
‘Ali ibn Abi Talhah said, narrating from Ibn ‘Abbas concerning the words {And do not marry Al-Mushrikat (idolatresses) till they believe (worship Allah Alone)}: Allah excludes from that the women of the people of the Book. This was also the view of Mujahid, ‘Ikrimah, Sa`id ibn Jubayr, Makhul, Al-Hasan, Ad-Dahhauak, Zayd ibn Aslam, Ar-Rabi` ibn Anas and others. And it was said that what is meant is the mushrikun who worship idols, and it does not mean the people of the Book at all. This meaning is close to the first meaning. And Allah knows best.” (Tafsir Ibn Kathir, 1/474)
Lawful in marriage, intercourse in Islamic law is via lawful marriage or “ what the right hand possess”