'About this time the King learned that the inhabitants of two hilly tracts, denominated Kuriat and Nardein, continued the worship of idols and had no… - Mohammed Qacim Ferichta

“First question. “From what description of Hindoos is it lawful to exact obedience and tribute?” Answer – It is lawful to exact obedience and tribute from all infields, and they can only be considered as obedient who pay the poll tax and tribute without demur, even should it be obtained by force; for, according to the law of Prophet, it is written, regarding infields “Tax them to the extent that they can pay, or utterly destroy them.’ The learned of the faith have also enjoined the followers of Islam, “To slay them, or to convert them to faith;’ a maxim conveyed in the words of the Prophet himself. The Imam Huneef, however, subsequently considered as poll tax, or as heavy a tribute imposed upon them as they can bear, may be substituted for death, and he has accordingly forbidden that their blood heedlessly spilt. So that it is commanded that the Juzeea (poll-tax) and Khiraj (tribute) should be exacted to the uttermost farthing from them, in order that the punishment may approximate as nearly as possible to death.” (p. 198)

In 1018 CE Mahmud attacked the holy town of Mathura, the land of Lord Krishna, considered one of the richest in the northern belt, after the abject surrender of the Gurjara Pratihara ruler Rajyapala. Just to give an idea of the amount of loot that Mahmud managed to ship back to Ghazni during each of his plunders of India, this is the account of his campaign in Mathura by Ferishta:
It is said that the Sultan found in Muttra [Mathura] five great idols of pure gold, with eyes of rubies, each of which eyes was worth fifty thousand dinars. Upon another idol, he found a sapphire, weighing four hundred miskal; and the image being melted down, produced ninety eight thousand three hundred miskal of pure gold. Besides these, there were above a hundred idols of silver, which loaded a hundred camels with bullion. The Sultan having tarried here twenty days, in which time the city suffered greatly from fire, besides what it suffered from the hand of ravage and desolation, he marched against the other fortified places in these districts …

“In the year 402 Mahmud resolved on the conquest of Thanesar, in the kingdom of Hindustan. It had reached the ears of the king that Thanesar was held in the same veneration by idolaters, as Mecca by the faithful; that there was an old temple there, in which they had set up a number of idols, the principal of which was called [p. 30] Jagsom, and was believed to have existed over since the creation of the world. When Mahmud reached the Panjab, he was desirous that, in accordance with the subsisting treaty with Anandpal, no injury should be sustained by that prince’s country, in consequence of the Muhammadan army passing through it. An embassy was accordingly sent to inform the Raja of his design against Thanesar, and desiring him to depute his officers to remain with the army, in order that the villages and towns which belonged to him might be protected from the camp followers.