SB 9.1.26
tasmin pravista evasau
sudyumnah para-vira-ha
apasyat striyam atmanam
asvam ca vadavam nrpa
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
O King Pariksit, as soon as Sudyumna, who was expert in subduing enemies, entered the forest, he saw himself transformed into a female and his horse transformed into a mare.