Why is the Sacred Heart on fire?

The image of the Sacred Heart on fire is directly from the private revelations of St. Margaret Mary Alacoque, but is also very biblical.

Assassinated for Consecrating His Country to the Sacred Heart - Sacred Windows

Clipart of a 3d Sacred Heart with Fire Thorns and a Cross - Royalty Free Vector Illustration by AtStockIllustration #1466383

What is the meaning of the Sacred Heart and the Immaculate Heart?

Abstract Academia

Fire - City of Sacred Heart

Why Is the Sacred Heart Burning?

An Orthodox Analysis of the “Sacred Heart” Worship • Patristic Faith

Why is the Sacred Heart on fire?

Sacred Heart - Wikipedia

What the world needs now: To burn with the love of Christ's Sacred Heart – Catholic World Report