We Catholics disagree with our Protestant brethren when they contend that no good works resulting from and caused by grace are meritorious, as the proof of genuine faith, or that none of them can play a role in our ultimate salvation, as the “fruit” of faith or “work of faith” (1 Thessalonians 1:3; 2 Thessalonians 1:11) or “faith working through love” (Galatians 5:6) or “good works, which God prepared beforehand, that we should walk in them” (Ephesians 2:10), as “God’s fellow workers” (1 Corinthians 3:9), “working together with” God (2 Corinthians 6:1), and working “harder” as a result of “the grace of God which is with” us (1 Corinthians 15:10), “abounding in the work of the Lord” (1 Corinthians 15:58), since “God is at work in” us, “both to will and to work for his good pleasure” (Philippians 2:13).

Is the prophet Isaiah’s overall soteriological teaching closer to Catholic or Protestant teaching? We’ll examine that question (all passages are from the Revised Standard Version). 

Isaiah teaches that God draws all sinners by his grace, without which no one is, or can be saved, and there are passages hinting at the New Testament doctrines of justification, faith, grace and salvation, as well as about God’s love and mercy and forgiveness:

• “Though your sins are like scarlet, they shall be as white as snow; though they are red like crimson, they shall become like wool” (1:18; cf. 33:24; 44:21-22; 54:7-8; 55:7; 60:10);
• “Behold, God is my salvation; I will trust, and will not be afraid” (12:2; cf. 17:10; 26:3-4);
• “Let us be glad and rejoice in his salvation” (25:9);
• “In returning and rest you shall be saved; in quietness and in trust shall be your strength” (30:15; 50:10);
• “The LORD waits to be gracious to you ... to show mercy to you” (30:18); 
• “The LORD is our king; he will save us” (33:22; cf. 35:4; 37:20; 38:20);
• “Your Redeemer is the Holy One of Israel” (41:14; cf. 43:1, 14; 44:6, 22-24; 47:4; 48:17, 20; 49:7; 52:9; 54:5, 8; 60:16; 63:9, 16);
• “I am the LORD your God, the Holy One of Israel, your Savior” (43:3; cf. 43:11; 45:15; 49:26; 60:16);
• “There is no other god besides me, a righteous God and a Savior. ... Turn to me and be saved, all the ends of the earth!” (45:21-22);
• “By his knowledge shall the righteous one, my servant, make many to be accounted righteous; and he shall bear their iniquities” (53:11);
• “I will heal him; I will lead him and requite him with comfort” (57:18);
• “I will faithfully give them their recompense, and I will make an everlasting covenant with them” (61:8);
• “he has clothed me with the garments of salvation, he has covered me with the robe of righteousness” (61:10);
• “I will recount the steadfast love of the LORD …  according to all that the LORD has granted us, and the great goodness to the house of Israel which he has granted them according to his mercy, according to the abundance of his steadfast love” (63:7).

Thus far, Catholics and Protestants agree. But Isaiah also regards works — as Catholics do — in necessary conjunction with faith (rejection of “faith alone”), and part and parcel of the process of salvation:

• 1:16-17, 19-20 Wash yourselves; make yourselves clean; remove the evil of your doings from before my eyes; cease to do evil, learn to do good; seek justice, correct oppression; defend the fatherless, plead for the widow. … “If you are willing and obedient, you shall eat the good of the land; but if you refuse and rebel, you shall be devoured by the sword ...” (cf. 1:13-15, 21, 23, 26-27)
• 3:10-11 Tell the righteous that it shall be well with them, for they shall eat the fruit of their deeds. Woe to the wicked! It shall be ill with him, for what his hands have done shall be done to him. (cf. 10:1-3; 29:20)
• 26:2 Open the gates, that the righteous nation which keeps faith may enter in.
• 26:12 O LORD, thou wilt ordain peace for us, thou hast wrought for us all our works.
• 32:17 And the effect of righteousness will be peace, and the result of righteousness, quietness and trust forever.
• 33:15-16 He who walks righteously and speaks uprightly, who despises the gain of oppressions, who shakes his hands, lest they hold a bribe, who stops his ears from hearing of bloodshed and shuts his eyes from looking upon evil, he will dwell on the heights; his place of defense will be the fortresses of rocks; his bread will be given him, his water will be sure. (cf. 56:1-2; 57:1-2)
• 38:3 “I have walked before thee in faithfulness and with a whole heart, and have done what is good in thy sight.”
• 48:18-19 O that you had hearkened to my commandments! Then your peace would have been like a river, and your righteousness like the waves of the sea; your offspring would have been like the sand, and your descendants like its grains; their name would never be cut off or destroyed from before me.”
• 64:5 Thou meetest him that joyfully works righteousness, those that remember thee in thy ways. …
• 59:2 But your iniquities have made a separation between you and your God, and your sins have hid his face from you so that he does not hear.
• 59:11-12, 18 We look for justice, but there is none; for salvation, but it is far from us. For our transgressions are multiplied before thee, and our sins testify against us; for our transgressions are with us, and we know our iniquities. … According to their deeds, so will he repay …
• 65:7 “Because they burned incense upon the mountains and reviled me upon the hills, I will measure into their bosom payment for their former doings.”