What is the spiritual reward for performing Hajj on behalf of one's parents?

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When a person performs Hajj on behalf of both parents, it is accepted from him and from them, their spirits rejoice in heaven, and he is recorded with Allah as being dutiful (birr). Moreover, whoever performs Hajj for his parents, or settles a debt owed by them, he will be resurrected on the Day of Judgment among the dutiful ones. Whoever performs Hajj for his father or mother has fulfilled their obligation, and he will receive the virtue equivalent to ten Hajj pilgrimages. These narrations are reported by Ad-Daraqutni.