Payement of interest on loan taken in cash allowed ??

A takes loan from B of Rs. 500000 through Bank transfer. At the end of the year, A pays to B interest of rs.63000(70000-7000) in CASH after deducting 10% TDS i.e 7000. My doubt is that whether A can pay interest of 63000 in cash or he has to pay it via Bank only...??