Maliks Muwatta Book 20, Hadith Number 180.

Section : Sending Women and Children Ahead.

Yahya related to me from Malik from Nafj from Salim and Ubaydullah, two sons of Abdullah ibn Umar, that their father Abdullah ibn Umar used to send his family and children from Muzdalifa to Mina ahead of him so that they could pray subh at Mina and throw the stones before everyone (else) arrived.