וַיֹּ֨סֶף ע֥וֹד דָּוִ֛ד אֶת־כָּל־בָּח֥וּר בְּיִשְׂרָאֵ֖ל שְׁלֹשִׁ֥ים אָֽלֶף׃
大衛又召集以色列所有精選的人，共三萬人。
Rashi
All the chosen men of Yisroel, thirty thousand. Because they gathered for him when they crowned him in Chevron and [therefore] this was a second gathering [for Dovid] [Scripture] herefore says, "[Dovid] again gathered."
Tze'enah Ure'enah
“David again assembled all the picked men of Israel, thirty thousand” [6:1]. Many people of Israel assembled and they made David king in the city of Hebron. Now, when David wanted to move the Ark from the house of Avinadav to God’s house, he assembled thirty thousand young men.