وَصِفَةُ التَّمَتُّعِ: أَنْ يَبْتَدِئَ مِنَ الْمِيقَاتِ فَيُحْرِمَ بِعُمْرَةٍ
Translation: The procedure of tamattu begins at the miqat, where the pilgrim enters ihram for Umrah.
Yabtadiʾa means “to begin.” The first rite is Umrah, not Hajj: the pilgrim enters ihram for Umrah at the miqat. Hajj is entered separately later.