11 “For nothing You shall save them”. He has taught us even for these very men to pray. However “they shall sojourn and hide,” however deceitful they be, however dissemblers and liers in wait they be; do thou pray for them, and do not say, Shall God amend even such a man, so evil, so perverse? Do not despair: give heed to Him whom you ask, not him for whom you ask. The greatness of the disease do you see, the might of the Physician do you not see? “They shall sojourn and hide: as my soul has undergone.”
Undergo, pray: and there is done what? “For nothing You shall save them.” You shall make them safe so as that nothing to You it may be, that is, so that no labour to You it may be. With men they are despaired of, but Thou with a word dost heal; You will not toil in healing, though we are astounded in looking on. There is another sense in this verse, “For nothing You shall save them:” with not any merits of their going before You shall save them....They shall not bring to You he-goats, rams, bulls, not gifts and spices shall they bring You in Your temple, not anything of the drink-offering of a good conscience do they pour thereon; all in them is rough, all foul, all to be detested: and though they to You bring nothing whereby they may be saved; “For nothing You shall save them,” that is, with the free gift of Your Grace....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)