Rynning was born in Kastnes in the
prestegjeld of
Tranøy (now part of
Dyrøy Municipality). He was the son of Ole Rynning, who served as the bailiff () in Senja and
Tromsø, and his wife Golla Hveding. Rynning married a daughter of the rural shopkeeper Bernt Anker Steen in Ringsaker. In 1796 he enrolled in the
Trondheim Cathedral School, and he received his
cand.theol. degree from the
University of Copenhagen in 1800. In addition to theology, had also studied other topics that he thought could be useful as a priest and teacher of the people, such as agriculture. His interest in such practical matters made him a typical example of a so-called "
potato priest" (). In Norway, he worked as a Sunday school teacher in Trondheim for a time and as a tutor at the home of Eiler Hagerup Holtermann at the
Austrått Manor. He took a position in Copenhagen as an applicant for public office in 1805, and was then appointed a traveling curate in Ringsaker in the same year. In 1817, he became parish priest in the same place. Rynning did much to improve schooling in Ringsaker. In 1824 he was appointed parish priest in Snåsa, where he remained the rest of his life. Rynning died in Snåsa. He was the grandfather of
Bernt Julius Muus (1832–1900), who helped found
St. Olaf College in
Northfield, Minnesota. ==Publications and distinctions==