You wouldn’t tell your children, “Bathe regularly; if necessary, use water.”
Nor would you advise a friend, “Be a faithful husband; if necessary, love your wife.”
Those redundant instructions defy logic. They also beg the question about what other means you would employ to accomplish those goals. You might as well tell someone, “Stay alive; if necessary, breath oxygen.”
And yet many Christians rally around a similarly illogical statement when it comes to evangelism. “Preach the gospel; if necessary, use words,” is a mantra that is a darling of social gospel activists. That quote, wrongly attributed to Francis of Assisi, is wielded when it’s time to poke zealous evangelists in the eye, or rebrand social work as a form of evangelism. Social gospel advocates like Rick Warren  Rick Warren, 40 Days of Community: Better Together Devotional: What on Earth Are We Here For? (Grand Rapids: Zondervan, 2010) 61. and Jim Wallis https://sojo.net/about-us/news/pope-francis-message-washington love to use it.
And let’s face it, there is a winsome ring of truth to the idea that my lifestyle can be a testimony of God’s saving work. Moreover, there is a built-in rebuke of evangelists who fail to walk their talk. Their hypocrisy—faith without works—is a reproach on God, His Word, and His people (James 2:14–17). But it’s absurd to turn that hypocrisy into an argument for the primacy of good works apart from the clear proclamation of the gospel.
The Necessity of Words
Paul never said, “How will they see without a preacher?” He said, “How will they hear without a preacher” (Romans 10:14). That is because every time the word “preach” appears in the New Testament it refers to vigorous verbal proclamation. It is verbal in its testimony of the works of a Savior who fulfilled the law that we have continually broken (Matthew 5:17–18; Romans 3:23), suffered the punishment that we could never bear (Isaiah 53:4–6; 1 Peter 2:24), and defeated the grave (2 Timothy 1:10; Hebrews 2:14).
And because Christ’s people depend entirely upon Hisuniquework done on their behalf (2 Corinthians 5:21), there is no way to fully demonstrate it through actions alone. As Voddie Baucham points out: “For me to think that I can live the gospel is to put myself in the place of Christ.”  https://www.youtube.com/watch?v=2Rd2WiYyDxs
So where does that leave works of social justice such as feeding the hungry, clothing the poor, and caring for the oppressed? No one would argue that they are bad things to do. Indeed James defines them as integral to pure religion (James 1:27). But do those acts of mercy have any role to play in a person’s salvation?
Advocates of the social gospel argue yes, and appeal to Matthew 25 as their apex argument:
Then the King will say to those on His right, “Come, you who are blessed of My Father, inherit the kingdom prepared for you from the foundation of the world. For I was hungry, and you gave Me something to eat; I was thirsty, and you gave Me something to drink; I was a stranger, and you invited Me in; naked, and you clothed Me; I was sick, and you visited Me; I was in prison, and you came to Me.” Then the righteous will answer Him, “Lord, when did we see You hungry, and feed You, or thirsty, and give You something to drink? And when did we see You a stranger, and invite You in, or naked, and clothe You? When did we see You sick, or in prison, and come to You?” The King will answer and say to them, “Truly I say to you, to the extent that you did it to one of these brothers of Mine, even the least of them, you did it to Me.”
Then He will also say to those on His left, “Depart from Me, accursed ones, into the eternal fire which has been prepared for the devil and his angels; for I was hungry, and you gave Me nothing to eat; I was thirsty, and you gave Me nothing to drink; I was a stranger, and you did not invite Me in; naked, and you did not clothe Me; sick, and in prison, and you did not visit Me.” Then they themselves also will answer, “Lord, when did we see You hungry, or thirsty, or a stranger, or naked, or sick, or in prison, and did not take care of You?” Then He will answer them, “Truly I say to you, to the extent that you did not do it to one of the least of these, you did not do it to Me.” These will go away into eternal punishment, but the righteous into eternal life. (Matthew 25:34–46)
Was Jesus saying that our eternal destinies hinge on feeding the hungry, housing the homeless, clothing the naked, and visiting the oppressed? And how would that square with salvation by grace through faith apart from works (Ephesians 2:8-9)?
The Whole [Other] Gospel
Tony Campolo is one of the most prominent advocates for the social gospel. His handling of Matthew 25 typifies the wider movement. While not explicitly denying the gospel of grace alone, he argues that it is our treatment of the poor and oppressed that will determine our eternity:
I place my highest priority on the words of Jesus, emphasizing the 25th chapter of Matthew, where Jesus makes clear that on Judgment Day the defining question will be how each of us responded to those he calls “the least of these.”  http://tonycampolo.org/for-the-record-tony-campolo-releases-a-new-statement/#.Vg4Hbnh7DxM
The recently closed Evangelical Association for the Promotion of Education (EAPE), of which Campolo was founder and president, clearly defines who he thinks “the least of these” are:
That Jesus was homeless and taught that we may encounter Him in “the least of these”—the hungry, thirsty, naked, sick, widow, stranger and imprisoned (Matthew 25:35-40), is the basis of what Tony calls the Whole Gospel and informs EAPE’s holistic ministry. And it raises questions for the Church and every Christian: what should be our response to the homeless and to “the least of these”?  http://eape.org/tag/matthew-2535-40-rich-mullins/
Note Campolo’s use of the term “Whole Gospel.” He is implying that proclamation of the good news is only a partial gospel and must be accompanied by social action in order to become a complete or “whole” gospel. But his imbalanced emphasis betrays his mishandling of Matthew 25:35–40.
The Bible repeatedly teaches that good works are ultimately God’s works because they are the natural fruit of salvation; never the cause (cf. Ezekiel 36:25-27; James 2:14–17). And in Matthew 25 you don’t see judgment based on works, you see works revealing who is truly saved by faith. John MacArthur is emphatic on this point:
The good deeds commended in Matthew 25:35–36 are the fruit, not the root, of salvation. It cannot be emphasized too strongly that they are not the basis of entrance into the kingdom. Christ will judge according to works only insofar as those works are or are not a manifestation of redemption, which the heavenly Father has foreordained. If a person has not trusted in Jesus Christ as Lord and Savior, no amount of seemingly good works done in His name will avail to any spiritual benefit.  John MacArthur, The MacArthur New Testament Commentary: Matthew 24–28 (Chicago: Moody Publishers, 1989) 122.
Who’s Who Among the Judged
Another critical issue in understanding Matthew 25 is to recognize that the division Christ makes is not between the church and the pagan world, but between true and false Christians. While the pagan lives in open unbelief, the false Christian is an imposter who has blended in among God’s people. False Christians are the recipients of Christ’s most terrifying judgment:
So then, you will know them by their fruits. Not everyone who says to Me, “Lord, Lord,” will enter the kingdom of heaven, but he who does the will of My Father who is in heaven will enter. Many will say to Me on that day, “Lord, Lord, did we not prophesy in Your name, and in Your name cast out demons, and in Your name perform many miracles?” And then I will declare to them, “I never knew you; depart from Me, you who practice lawlessness.” (Matthew 7:20–23)
Matthew 25:34-46 makes a similar division between those who have genuine faith and those whose faith is false, according to the evidence of their works. Note carefully that both groups of people think they are Christians because they address Jesus as “Lord” (Matthew 25:37, 44). Both groups are also surprised by the verdict. The surprise reveals humility among Christ’s people (“when did we,” Matthew 25:37–39) and self-righteousness among those who are faking it (“when did we . . . not,” Matthew 25:44).
Who’s Who Among the Lowly
Finally, the beneficiaries of these good works are not the disenfranchised people of the world, as Campolo suggests. The word “brothers” (Matthew 25:40) is vital to understanding where our benevolence is to be directed. Jesus is saying that the fruit of genuine faith is evidenced in the way we care for fellow believers who are suffering (cf. John 13:35; 1 John 3:10–11). MacArthur brings this point home:
The King’s addressing these people as brothers of Mine gives still further evidence that they are already children of God. . . . Because of their identity with Christ, they will often be hungry, thirsty, without decent shelter or clothing, sick, imprisoned, and alienated from the mainstream of society. The MacArthur New Testament Commentary: Matthew 24–28, 124–125.
This is not to deny any duty we have to love the disenfranchised people of the world. But if proponents of the social gospel were serious about Scripture, they would target passages that refer to loving our neighbors—even loving our enemies (Matthew 22:39; 5:44). Christ’s words in Matthew 25 have nothing to do with the social justice they advocate.
Matthew 25:34–46 was never written as a blueprint for salvation through social work nor should it be employed as such. It’s not an argument for preaching the gospel through our actions alone, but rather that our actions authenticate the gospel we preach. And those actions must be prioritized towards our suffering fellow believers. So please, care for other believers because Jesus commanded us to. Realize that a lack of care may point to a lack of saving faith. And preach the gospel with words because they’re always necessary.