He then marched and encamped under the fort of Delhi... The city and its vicinity were freed from idols and idols-worship, and in the sanctuaries of … - Qutb-ud-din Aibak

Qutb-ud-Din Aybak also is said to have destroyed nearly a thousand temples, and then raised mosques on their foundations. The same author states that he built the Jami Masjid, Delhi, and adorned it with the stones and gold obtained from the temples which had been demolished by elephants, and covered it with inscriptions (from the Quran) containing the divine commands. We have further evidence of this harrowing process having been systematically employed from the inscription extant over the eastern gateway of this same mosque at Delhi, which relates that the materials of 27 idol temples were used in its construction.

The first of these bloody sultans, Kutb-d Din Aibak, was a normal specimen of his kind—fanatical, ferocious and merciless. His gifts, as the Mohammedan historian tells us, “were bestowed by hundreds of thousands, and his slaughters likewise were by hundreds of thousands.” In one victory of this warrior (who had been purchased as a slave), “fifty thousand men came under the collar of slavery, and the plain became black as pitch with Hindus.”

About this time they wrote to the heavenly throne, that the Rai who had fled from Dehli had raised an army of idolatrous, turbulent, and rebellious tribes, the vapour of pride and conquest havingentered his thoughtless brain." Kutbu-d din pursued him, " and when the wretch was taken, his head was severed from his body and sent to Dehli, which had been his residence and capital." Kutbu-d din then himself returned to Dehli, and sent " written accounts of his capture of forts and strongholds, and his victories and holy wars" to Ghazna, to which capital he was invited to receive thanks in person from Muizzu-d din Sam Ghori.