Vaisesika Sūtra 5.1.01

आत्मसंयोगप्रयत्नाभ्यां हस्ते कर्म ॥१॥

ātmasaṁyogaprayatnābhyāṁ haste karma ॥1॥

[आत्म-संयोग-प्रयत्नाभ्यां (ātma-saṁyoga-prayatnābhyām) - by conjunction of ātma and effort; हस्ते (haste) - in the hand; कर्म (karma) - movement;]

Movement in the hand is due to conjunction of ātma and effort.