Liberation Of Kubera's sons from curse

Sri Krishna liberated from two Arjuna trees, the two sons of Kubera who, in their previous lives, had been turned into trees, by Narada’s curse. This is their story:

Once it so happened that these two brothers named Nalakubera and Manigreeva were so enamored of their wives that they did not notice the arrival of the great sage Narada. Insulted by this behavior, Narada cursed them thus: “You shall remain as two trees in Gokula forever.” Hearing this, the wives of Nalakubera and Manigreeva fell at the sage’s feet and asked him to forgive their husbands and take back his curse. Narada relented and said, ”A curse once given cannot be retracted. It can only be modified or lessened. Your husbands will be released by Lord Vishnu himself when he incarnates as Krishna.”

Krishna was dragging the wooden-mortar to which he had been tied by his mother Yashodha. As he passed between the trees, the mortar stuck in between. With a mighty heave, little Krishna pulled it forward; the force of the pull uprooted the trees and they crashed to the ground. Two heavenly beings in resplendent clothes appeared as if from the trees and paid their respects to Lord Krishna. Seeking his permission they returned to their heavenly abode. Thus were Kubera's sons released from Narada's curse. 

Hearing the loud crash of the trees, everyone rushed to the site. Nanda Maharaja untied the knots to free his child and picked him up with great relief and affection. He was glad that the falling trees had not hurt his baby and he liberally gave in charity to the needful, as his thanks-giving.