Short answer. Upon finality of the court's order confirming the sale — or, where the law allows redemption, upon expiration of the redemption period. Rule 68, Section 3 then entitles the purchaser or last redemptioner to possession, unless a third party actually holds the property adversely to the judgment obligor, and a writ of possession may issue on motion.
What the law says
Upon the finality of the order of confirmation or upon the expiration of the period of redemption when allowed by law, the purchaser at the auction sale or last redemptioner, if any, shall be entitled to the possession of the property unless a third party is actually holding the same adversely to the judgment obligor.
Rule 68, Section 3 — Sale of mortgaged property; effect. Read the full provision →
Confirmation is the hinge
In a judicial foreclosure, the auction is not the finish line. The sale happens because the defendant, after being ordered to pay, fails to pay the amount of the judgment within the period specified, and it is conducted in the manner and under the provisions of Rule 39 and other regulations governing sales of real estate under execution. But the transfer of rights waits for the court: only when confirmed by an order of the court does the sale operate to divest the rights in the property of all the parties to the action and to vest their rights in the purchaser.
When possession follows
Possession has its own trigger sentence: Upon the finality of the order of confirmation or upon the expiration of the period of redemption when allowed by law, the purchaser at the auction sale or last redemptioner, if any, shall be entitled to the possession of the property. Two different clocks, depending on the case. Where no redemption is allowed, the buyer's entitlement ripens when the confirmation order becomes final. Where the law does allow redemption, the buyer waits out the redemption period — and if someone redeems along the way, it is the last redemptioner who ends up entitled.
The adverse third-party exception
The section carves out one situation: possession follows unless a third party is actually holding the same adversely to the judgment obligor. The exception is about whose right the occupant claims. A person holding the property under the debtor stands in the debtor's shoes; a person actually holding it in their own claimed right — adversely to the debtor — cannot simply be swept out by the foreclosure's possession machinery, and their claim has to be dealt with on its own terms. For buyers, an occupied property therefore deserves scrutiny before bidding, not after.
The writ of possession, and prior encumbrances
Enforcement is by motion: the purchaser or last redemptioner may secure a writ of possession, upon motion, from the court which ordered the foreclosure — the same case, not a new one. One more limit sits earlier in the section: the sale shall not affect the rights of persons holding prior encumbrances upon the property or a part thereof. A buyer at a judicial foreclosure should therefore read the title the way the section does — confirmation transfers the parties' rights, but earlier encumbrances survive, and what exactly was acquired depends on what the mortgagor's side actually had.