SB 10.1.53
prasanna-vadanambhojo
nrsamsam nirapatrapam
manasa duyamanena
vihasann idam abravit
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Vasudeva’s mind was full of anxiety because his wife was facing danger, but in order to please the cruel, shameless and sinful Kamsa, he externally smiled and spoke to him as follows.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Sometimes one must act duplicitously in a dangerous position, as Vasudeva did to save his wife. The material world is complicated, and to execute one’s duties, one cannot avoid adopting such diplomacy. Vasudeva did everything possible to save his wife for the sake of begetting Krsna. This indicates that one may act duplicitously for the purpose of saving Krsna and His interests. According to the arrangement already foretold, Krsna was to appear through Vasudeva and Devaki to kill Kamsa. Vasudeva, therefore, had to do everything to save the situation. Although all the events were prearranged by Krsna, a devotee must try his best to serve the purpose of Krsna. Krsna Himself is all-powerful, but it is not that a devotee should therefore sit idly and leave everything to Him. This instruction is also found in Bhagavad-gita. Although Krsna was doing everything for Arjuna, Arjuna never sat down idly as a nonviolent gentleman. Rather, he tried his best to fight the battle and be victorious.