SB 4.15.1

maitreya uvāca
atha tasya punar viprair
 aputrasya mahīpateḥ
bāhubhyāṁ mathyamānābhyāṁ
 mithunaṁ samapadyata
Word for word: 
maitreyaḥ uvāca — Maitreya continued to speak; atha — thus; tasya — his; punaḥ — again; vipraiḥ — by the brāhmaṇas; aputrasya — without a son; mahīpateḥ — of the King; bāhubhyām — from the arms; mathyamānābhyām — being churned; mithunam — a couple; samapadyata — took birth.
Translation: 
The great sage Maitreya continued: My dear Vidura, thus the brāhmaṇas and the great sages again churned the two arms of King Vena’s dead body. As a result a male and female couple came out of his arms.