SB 4.12.23

sunanda-nandāv ūcatuḥ
bho bho rājan subhadraṁ te
 vācaṁ no ’vahitaḥ śṛṇu
yaḥ pañca-varṣas tapasā
 bhavān devam atītṛpat
Word for word: 
sunanda-nandau ūcatuḥ — Sunanda and Nanda said; bhoḥ bhoḥ rājan — O dear King; su-bhadram — good fortune; te — unto you; vācam — words; naḥ — our; avahitaḥ — attentively; śṛṇu — hear; yaḥ — who; pañca-varṣaḥ — five years old; tapasā — by austerity; bhavān — you; devam — the Supreme Personality of Godhead; atītṛpat — greatly satisfied.
Translation: 
Nanda and Sunanda, the two confidential associates of Lord Viṣṇu, said: Dear King, let there be all good fortune unto you. Please attentively hear what we shall say. When you were only five years old, you underwent severe austerities, and you thereby greatly satisfied the Supreme Personality of Godhead.
Purport: 

What was possible for Dhruva Mahārāja is possible for anyone. Any five-year-old child can be trained, and within a very short time his life will become successful by realization of Kṛṣṇa consciousness. Unfortunately, this training is lacking all over the world. It is necessary for the leaders of the Kṛṣṇa consciousness movement to start educational institutions in different parts of the world to train children, starting at the age of five years. Thus such children will not become hippies or spoiled children of society; rather, they can all become devotees of the Lord. The face of the world will then change automatically.