In this excerpt from the Panchavimsha Brahmana of the Sama Veda, aka the Tandya Mahabrahmana, a certain Yagna which can only performed in Kurukshetra is described. The Panchavimsha Brahmana mentions a story which demonstrates the greatness of Kurukshetra:
Indra and Rushama made a wager: "Whichever of us shall first run round the earth shall be the winner." Indra ran round the earth, Rushama ran round Kurukshetra (only). She said "I have conquered thee." But Indra said "It is I that have conquered thee." They went to the Gods for a decision. The Gods said: "Kurukshetra is as great as the vedi of Prajapati." So neither of the two won.
This story bears a striking resemblance to the famous story of Shiva's sons Kartikeya and Ganesha having a footrace around the world. Kartikeya runs around the world, whereas Ganesha just circumambulates his parents Shiva and Parvati. Because parents are considered to be the world of the son, Ganesha is declare the winner and is given the desired reward (either getting to be married first in North Indian versions, or getting a Jnana fruit in South Indian versions).
But my question is, who is this woman Rushama who had a race with Indra? And what was the purpose of the bet?
If it helps, a male figure named Rushama is mentioned in verse 12 of Rig Veda Book 8 Hymn 3:
śaghdhī no asya yad dha pauramāvitha dhiya indra siṣāsataḥ |
śaghdhi yathā ruśamaṃ śyāvakaṃ kṛpamindra prāvaḥ svarṇaram ||
Help for us, Indra, as thou helpest Paura once, this man's devotions bent on gain.
Help, as thou gavest Ruśama and Śyāvaka and Svarṇara and Kṛpa aid.
But I'm not sure if the male Rushama has any connection with the female Rushama. In any case, does anyone know if any other scriptures discuss Indra's race with Rushama?