Sentence:  The <WSD>De Profundis</WSD> is therefore a cry of hope, a prayer of love coming forth from the Sacred Heart to be re-echoed by our own; and whilst hoping for ourselves, we must hope also for our suffering brethren in purgatory, and we have confidence that if we pray with our whole hearts, our merciful Lord will soon deliver these souls, still dearer to Him than ourselves, and will admit them perfectly purified into peace and eternal rest. 
Meaning of the word marked with <WSD> tags:  The 130th psalm, one of the seven penitential psalms of the Roman Catholic and Anglican churches.