The pop star also promised to lead his new family with "honor and integrity, letting Jesus through his Holy Spirit guide us in everything we do..."
Posting a picture of the couple on Instagram, the 24-year-old said: "God's timing really is literally perfect, we got engaged on the seventh day of the seventh month, the number seven is the number of spiritual perfection, it's true, GOOGLE IT! Isn't that nuts?"
Hailey Baldwin, who is the daughter of actor and out-spoken Christian Stephen Baldwin, told supporters she was "utterly grateful to God" for her relationship with Justin.
She wrote on Twitter: "Not sure what I did in life to deserve such happiness but I am so utterly grateful to God for giving me such an incredible person to share my life with! No words could ever express my gratitude."
Bieber had previously been in a relationship with fellow singer Selena Gomez. The pair reportedly underwent Christian couples counselling last year with Carl Lenz, the 38-year-old pastor of Hillsong Church in New York - which Bieber has been attending.
His post on Instagram continued: "Was gonna wait a while to say anything but word travels fast, listen plain and simple Hailey I am soooo in love with everything about you! So committed to spending my life getting to know every single part of you loving you patiently and kindLY.
"I promise to lead our family with honor and integrity letting Jesus through his Holy Spirit guide us in everything we do and every decision we make. My heart is COMPLETELY and FULLY YOURS and I will ALWAYS put you first! "
Bieber has become increasingly vocal about his Christian faith since we was baptised in a bathtub by Pastor Lenz four years ago, quoting from the Bible and sermons on his social media pages on numerous occasions.
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