SB 3.1.30
kaccid dhareh saumya sutah sadrksa
aste ’grani rathinam sadhu sambah
asuta yam jambavati vratadhya
devam guham yo ’mbikaya dhrto ’gre
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
O gentle one, does Samba fare well? He exactly resembles the son of the Personality of Godhead. In a previous birth he was born as Karttikeya in the womb of the wife of Lord Siva, and now he has been born in the womb of Jambavati, the most enriched wife of Krsna.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Lord Siva, one of the three qualitative incarnations of the Personality of Godhead, is the plenary expansion of the Lord. Karttikeya, born of him, is on the level of Pradyumna, another son of Lord Krsna. When Lord Sri Krsna descends into the material world, all His plenary portions also appear with Him to exhibit different functions of the Lord. But for the pastimes at Vrndavana, all functions are performed by the Lord’s different plenary expansions. Vasudeva is a plenary expansion of Narayana. When the Lord appeared as Vasudeva before Devaki and Vasudeva, He appeared in His capacity as Narayana. Similarly, all the demigods of the heavenly kingdom appeared as associates of the Lord in the forms of Pradyumna, Samba, Uddhava, etc. It is learned here that Kamadeva appeared as Pradyumna, Karttikeya as Samba, and one of the Vasus as Uddhava. All of them served in their different capacities in order to enrich the pastimes of Krsna.