SB 8.19.10
evam sa niscitya ripoh sariram
adhavato nirvivise ’surendra
svasanilantarhita-suksma-dehas
tat-prana-randhrena vivigna-cetah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Lord Vamanadeva continued: O King of the demons, after Lord Visnu made this decision, He entered the body of His enemy Hiranyakasipu, who was running after Him with great force. In a subtle body inconceivable to Hiranyakasipu, Lord Visnu, who was in great anxiety, entered Hiranyakasipu’s nostril along with his breath.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The Supreme Personality of Godhead is already in the core of everyone’s heart. isvarah sarva-bhutanam hrd-dese ’rjuna tisthati (Bg. 18.61). Logically, therefore, it was not at all difficult for Lord Visnu to enter Hiranyakasipu’s body. The word vivigna-cetah, “very anxious,” is significant. It is not that Lord Visnu was afraid of Hiranyakasipu; rather, because of compassion, Lord Visnu was in anxiety about how to act for his welfare.