SB 9.5.26
sri-suka uvaca
athambarisas tanayesu rajyam
samana-silesu visrjya dhirah
vanam vivesatmani vasudeve
mano dadhad dhvasta-guna-pravahah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Srila Sukadeva Gosvami continued: Thereafter, because of his advanced position in devotional life, Maharaja Ambarisa, who no longer desired to live with material things, retired from active family life. He divided his property among his sons, who were equally as qualified, and he himself took the order of vanaprastha and went to the forest to concentrate his mind fully upon Lord Vasudeva.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
As a pure devotee, Maharaja Ambarisa was liberated in any condition of life because, as enunciated by Srila Rupa Gosvami, a devotee is always liberated.
iha yasya harer dasye
karmana manasa gira
nikhilasv apy avasthasu
jivan-muktah sa ucyate
In Bhakti-rasamrta-sindhu, Srila Rupa Gosvami thus instructs that if one’s only desire is service to the Lord, he is liberated in any condition of life. Maharaja Ambarisa was undoubtedly liberated in any condition, but as an ideal king he accepted the vanaprastha order of retirement from family life. It is essential for one to renounce family responsibilities and fully concentrate on the lotus feet of Vasudeva. Therefore Maharaja Ambarisa divided the kingdom among his sons and retired from family life.