give the shirt off their back字面意思连衬衫都肯脱给人，引申为“倾囊相助，尽力帮忙”。

【例句】
I’d give you the shirt off my back to help you pay for your wedding.
为了资助你支付婚礼的费用，我会倾囊相助。

Jack is such a nice guy—he would give his shirt off his back to help you out.
杰克真是个大好人，他会竭尽所能地帮你。