Jessica Alba and husband Cash Warren welcome their third child on New Year's Eve.

Their days-old son, named Hayes Alba Warren, already knows how to ring in the New Year in style, as he arrived just hours before the clock struck 12.

"You showed up a few days early but we couldn't be any happier," gushed the now father of three in an Instagram post. "On your first day of life, I promise to love you, to cherish you, and to provide you with a sandbox full of dreams to explore. Welcome to the family my sweet baby Hayes!"

The 36-year-old actress added that their baby is the "best gift" to welcome 2018. "Cash and I feel so blessed. Haven and Honor are already obsessed with their new baby bro," she said in her own post showing the baby boy sound asleep.

The now family of five continues tradition by naming their third child with the same first letter as their older daughters -- Honor, 9, and Haven, 6.

A source close to the couple earlier told E! News that the couple has always planned to have a third child and they just waited for the right time to welcome another member of the family.

The insider added that family has been calling baby Hayes a "Christmas miracle," who they were all excited to meet.

Happy as they all are about the new addition to their family, Alba shared in an earlier interview with the Daily Mail that this will be it for their family of five.

"We're good - three is good," she told the media outlet, saying that Haven and Honor are so proud that they get to be big sisters. "Cash and I at night are like, 'What is it going to be like having another kid? What does that mean for our family dynamic?' We kind of both have butterflies."

Alba first revealed her third pregnancy back in July via a Boomerang post on Instagram, which shows her with one hand on her stomach and another hand holding up a balloon shaped as number 3.