151 The wound in Christ’s side, the wellspring of living water, remains open in the risen body of the Saviour. The deep wound inflicted by the lance and the wounds of the crown of thorns that customarily appear in representations of the Sacred Heart are an inseparable part of this devotion, in which we contemplate the love of Christ who offered himself in sacrifice to the very end. The heart of the risen Lord preserves the signs of that complete self-surrender, which entailed intense sufferings for our sake. It is natural, then, that the faithful should wish to respond not only to this immense outpouring of love, but also to the suffering that the Lord chose to endure for the sake of that love.
Source: Dilexit Nos (Vatican.va)