In the IG post shared Monday, Garth and his wife of almost 19 years are seen hand in hand in St. Paul, Minnesota, heading to a Habitat for Humanity building site to help out their pal Jimmy Carter's charitable venture -- the 2024 Jimmy & Rosalynn Carter Work Project.

The singer clearly had a great day, writing in the caption, "As they say, Home is the key and love never quits! To everyone building with us, today was a GREAT Day 1!!!"

It was a fantastic day for him then -- but Garth's now singing a different tune after being hit with a lawsuit yesterday from a woman who claims he raped her at a Las Vegas hotel in 2019. The woman says she worked as Trisha's makeup artist and hairstylist for years, then started working for Garth as well in 2017.

TMZ broke the story of his response ... Garth responded to the lawsuit later Thursday ... claiming he's been "hassled to no end with threats, lies, and tragic tales of what my future would be if I did not write a check for many millions of dollars."

Garth saw this coming, filing his own lawsuit against the woman about a month ago, accusing her of "extortion and defamation of character." He had filed it anonymously "for the sake of families on both sides."

In his suit, Garth claims the accuser knew she would seriously damage his career and reputation if she followed through on her allegations.

But Garth's made it clear ... "I trust the system, I do not fear the truth, and I am not the man they have painted me to be.”