Need information on tax exemptions

Hello I am 21 year old and I m studying b.com my father is a businessman and his annual income is 180000 my mother wanted to purchase a site in Bangalore from a housing society the price was 900000 there are 6 installments each for every half year and my mother applied for it and paid 750000 till now by selling her jewellery etc.. So we are not able to pay remaining amount and they told me that they will return that 750000 amount to us. So my question is my father is not a tax payer and if that amount of 750000 comes to my mother's account and if income tax department has asked us about the clarity about that amount then how should we answer to them because in my fathers we can save up to 100000 per annum and we sold our gold of around 400000 and we don't have any receipt of purchasing gold and from our savings so please help me how to answer to income tax department for the amount comes into my mother's account