In general, under the Islamic administration, mostly Christians and Jews were allowed to retain their property, their customs and their religion by paying a tax.
In the name of God, the merciful and compassionate. This is a document [granted] by ‘Abd al-‘Aziz ibn Musá ibn Nusair to Tudmir, son of Ghabdush, establishing a treaty of peace and the promise and protection of God and his Prophet may God bless him and grant him peace. We [‘Abd al-‘Aziz] will not set special conditions for him or for any among his men, nor harass him, nor remove him from power. His followers will not be killed or taken prisoner, nor will they be separated from their women and children. They will not be coerced in matters of religion, their churches will not be burned, nor will sacred objects be taken from the realm, [so long as] he [Tudmir] remains sincere and fulfills the [following] conditions that we have set for him. He has reached a settlement concerning seven towns […] He will not give shelter to fugitives, nor to our enemies, nor encourage any protected person to fear us, nor conceal news of our enemies. He and [each of] his men shall [also] pay one dinar every year, together with four measures of wheat, barley, fruit juice, vinegar, honey and olive oil
(the document is dated from the Muslim month of Rajab, in the year 94 of the Hijra [April 713]).
IBN ADARÍ, Kitab al-bayán al-mugrib fi ajbar muluk al Andalus wa l-Magrib, 13th century
Who do you think Abd al-Aziz and Tudmir were? Why should they be signing a treaty?
Tudmir was a Christian Visigoth count who fought for King Roderick at the Battle of Guadalete. Although he resisted the invading Arabs and Berbers, he was finally defeated and he made peace with the Muslim emir Abd al-Aziz ibn Musa ibn Nusair, the first governor of Al-Andalus. The peace treaty allowed Christians who submitted to Muslim rule to continue living with their families, practicing their faith and keeping their status. However, they were required to pay a tribute and to turn over any enemies of the conquerors to the new authorities. Probably, the region of Tudmir lost its political independence by the 780s, during the period of the Emirate of Cordoba.