How to tell boyfriend about the helping situation?

Hello. Need help on how to tell my boyfriend about the helping situation without making it sound offensive. Here's the story:

Few days ago, I told my boyfriend about my situation for the visa. I told him about the process and such. When I told him about the fee, he asked how much, and I told him. I wasn't thinking of asking him to pay for me cause my mom can handle it. He directly said that he would pay for the fee, and I kept asking him many times: "are you sure?" and he said he would. Later, when I told him that I would do the visa process thing the next day, and still willing to pay me, he told me he doesn't have enough cash in him. Felt disappointed, but I already expected it. Not because I was relying on him, but because he reassured me that he would.

I wanted to tell him about that it's okay to help but be sure that he could because I expected it. But I don't know how to bring it in words, in a kind way, so yeah.

How to tell boyfriend about the helping situation?
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