The illuminated initial F here opens the First Book of Kings (known more commonly today as the first book of Samuel) with the depiction of Samson and the lion. Samson, generously-tressed, is forcing the lion's mouth open with his bare hands and stands frozen in motion in front of a stylized mountain and tree just as he is about to rip the animal apart. This scene actually makes an unexpected (and likely erroneous) appearance here, as Samson's story is actually confined to the Book of Judges.
The illuminator of this miniature belongs to the generation of Bolognese masters working in the second half of the 13th century, who created the Primo Stile Bolognese known for echoing Byzantine traditions and quite commonly found in the Bibles made in the thriving university town. The vibrant palette and style of the figures on this and two sister leaves (also available at Dr. Jörn Günther Rare Books) are, moreover, quite idiosyncratic, which allowed for a clear association with a hand: the First Master of the Infortiatum dating c. 1270-1300 (Paris, BnF, ms. lat. 4476). The master, in comparison with the other two hands in that manuscript, has a linear style of figures and formed his borders with delicate foliage and small animals.