His wife-to-be wrote the letter to the 21-year-old suggesting he reflect on her message whenever he feels anxious, and Beckham has inked her words, underneath an existing tattoo of her eyes, onto his neck.
Peltz, a 26-year-old American actress, signed off the letter "your future wifey".
The tattoo reads: "My forever boy. Read this anytime you feel anxious. I want you to know how deeply loved you are.
"You have the kindest heart I've ever met and hope I never go a day without your love.
"I think you are so incredible. Just we can get through it all together if you breathe slow and trust. I love you beyond."
Beckham shared his new ink on Instagram, captioning the post "Love letters".
This is the 21-year-old's fifth tattoo tribute to his fiancée. The model and photographer also has Peltz's name and an image of her eyes tattooed on his neck.
The couple got engaged in July last year, six months after Beckham first shared a picture of the pair together on Instagram.
Last year, Beckham revealed he first met Peltz at Coachella in 2017 but that the couple had met again at a party in 2019 and "fell in love".
David Beckham's son announced his and Peltz's engagement on Instagram, alluding to wanting children with his fiancée in the future.
He wrote: "Two weeks ago I asked my soulmate to marry me and she said yes xx I am the luckiest man in the world. I promise to be the best husband and the best daddy one day ❤️ I love you baby xx".
Peltz shared the same image on her own Instagram, writing: "You've made me the luckiest girl in the world. I can't wait to spend the rest of my life by your side. Your love is the most precious gift. I love you so so much baby and thank you Harper for this pic."
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