The Dowry. It is permissible for the dowry to be teaching Quran, a ring of iron or anything else, a small or large amount, And it is recommended for it to be Five Hundred Dirham Sahih Muslim 1427 e
Translation
Abd al-Rahman b. 'Auf (Allah be pleased with him) reported that Allah's Messenger (ﷺ) saw the signs of the happiness of wedding in me, and I said
I have married a woman of the Ansar. He said: How much Mahr have you paid? I said: For a date-stone weight of gold. And in the hadith transmitted by Ishaq (it is): (nawat weight) of gold.