SB 3.19.16
tenettham ahatah ksattar
bhagavan adi-sukarah
nakampata manak kvapi
sraja hata iva dvipah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Hit in this manner by the demon, O Vidura, the Lord, who had appeared as the first boar, did not feel the least quaking in any part of His body, any more than an elephant would when struck with a wreath of flowers.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
As previously explained, the demon was originally a servitor of the Lord in Vaikuntha, but somehow or other he fell as a demon. His fight with the Supreme Lord was meant for his liberation. The Lord enjoyed the striking on His transcendental body, just like a fully grown-up father fighting with his child. Sometimes a father takes pleasure in having a mock fight with his small child, and similarly the Lord felt Hiranyaksa’s striking on His body to be like flowers offered for worship. In other words, the Lord desired to fight in order to enjoy His transcendental bliss; therefore He enjoyed the attack.