“Want. To. Eat. These. Toes.,” the 36-year-old singer captioned the post of Jacob’s small feet.
“Just do it,” singer Jessie James Decker joked in response.
“Nothing like baby feet,” wrote another.
“How cute & sweet is this? My heart is just bursting with happiness!” said a fan.
“Baby toes are the best toes,” commented another fan in response.
The “Cry Pretty” singer and her husband Mike Fisher welcomed their second child in January. Their firstborn son, Isaiah, was born in 2015 and is now 4 years old.
"Jacob Bryan Fisher entered the world in the wee hours of the morning on Monday," Underwood wrote on Instagram at the time. "His mom, dad and big brother couldn't be happier for God to trust them with taking care of this little miracle!"
She added: "Our hearts are full, our eyes are tired and our lives are forever changed. Life is good..."