This verse comes from the poem "One of the Six Songs under the Sai".
"One of the Six Songs under the Sai" is a work written by Li Bai in the Tang Dynasty. The full text is "It's snowy in the Tianshan Mountains in May, but there are no flowers, only cold. I hear broken willows in the flute, but I haven't seen the spring scenery. I fight with the golden drum at dawn, and hug the jade saddle at night. I would like to put the sword under my waist to kill the Loulan." Therefore, "I hope that with the sword hanging from my waist, I can kill Loulan directly" comes from this poem. This sentence means "I hope that with the sword hanging on my waist, I can quell the border leaks as soon as possible and make meritorious service to the country."