Sir,
According to Section 12 (3) of IGST Act, 2017, "the place of supply of services, -
(a) directly in relation to an immovable property, including services provided by architects, interior decorators, surveyors, engineers and other related experts or estate agents, any service provided by way of grant of rights to use immovable property or for carrying out or co-ordination of construction work; or
(b) by way of lodging accommodation by a hotel, inn, guest house, home stay, club or campsite, by whatever name called, and including a house boat or any other vessel; or
(c) by way of accommodation in any immovable property for organising any marriage or reception or matters related thereto, official, social, cultural, religious or business function including services provided in relation to such function at such property; or
(d) any services ancillary to the services referred to in clauses (a), (b) and (c),
shall be the location at which the immovable property or boat or vessel, as the case may be, is located or intended to be located :
In your case the service is deemed to be provided at the place where the immovable property is located. Since it is located in Delhi, you have to pay CGST and SGST. Even if the rent is collected from another person the said fact will not affect place of supply of service and gst is to be paid accordingly. Only drawback is XYZ cannot avail the credit of gst paid since he is located at Mumbai.