But in September he will have to get involved, the person would need to continue the contract with the landlord. By the way, does your original agreement allow for subletting? All the agreements I've seen expressly forbid it. If there is a clause there you might need to get it corrected in writing.

The worst case is not that the new dude does not pay for the 2 months remaining, the worst case is if he doesn't pay and stays to squat there after September, burns down the apartment, causes other damages. There is a chance you could be implicated in some way for that if you can be shown to have violated your own rent agreement, or be responsible for removing him. It takes a while to remove unpaying squatters through the court, no less than 60 days.

Here is the common wording forbidding subletting.

השוכר אינו רשאי להעביר זכויותיו כלפי הסכם זה, כולן או מקצתן, וכן אסור לו להשכיר את הדירה ו/או למסור את החפצים ו/או חלק מהם בין מוגדר ובין בלתי מוגדר וכן אסור לו למסור החזקה בדירה ולא להרשות לאחר לגור בה ולהשתמש בה או בחפצים או בחלק מהם, בין מוגדרים ובין לא מוגדרים ובין יחד עמו, ללא הסכמת המשכיר ו/או בא כוחו לכך.

For standard subletting agreements and more info search for "חוזה שכירות משנה" in Google.
https://webcache.googleusercontent.com/search?q=cache:HREJA2...

Assignment and Subletting Sample Clauses - Law Insider
https://www.lawinsider.com/clause/assignment-and-subletting
Assignment and Subletting. In the event that Tenant desires to encumber this Lease, assign this Lease or sublet all or any part of the Premises or grant any ...

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Note added at 11 hrs (2019-04-29 09:33:03 GMT)
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Sublease Agreement template
https://sa.berkeley.edu/legal/forms/sublease

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Note added at 11 hrs (2019-04-29 09:35:56 GMT)
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https://www.zillow.com/blog/subletting-legal-tips-178943/