Everyone who calls on the name of the Lord will be saved. (NIV)
The context of this verse in Romans makes it clear that the “Lord” referred to in this verse is the Lord Jesus Christ. However, this verse is a quotation from Joel 2:32 in the Old Testament, and in Joel the “Lord” is Yahweh. That has caused some Trinitarians to say that Jesus is God. The argument is not valid, however. There is nothing in the context or scope of Scripture that shows that Yahweh and Jesus Christ are the same being. What it shows is simple and straightforward: In the Old Testament, one called upon Yahweh for salvation, and now we call upon Jesus Christ for salvation. This does not show an identity of persons, rather it demonstrates a shift of responsibility. This responsibility that Jesus now has was foreshadowed in the Old Testament record of Joseph: the people would go to Pharaoh for their needs to be met, but after Pharaoh elevated Joseph to second-in-command, he told them, “Go to Joseph” (Gen. 41:55). No one would conclude that Pharaoh and Joseph were the same being, and there is no reason to conclude that Jesus and God are both “God” just because Jesus now has some of the responsibilities that God had until He exalted Jesus.
Part of the confusion surrounding this issue is that in the Old Testament, many versions do not print the name Yahweh, but instead say “Lord.” Although God never commanded it, it was the custom of the Jews, out of reverence for God, not to pronounce the name of God, so they wrote “Lord” when the Hebrew text said Yahweh. Many Christian Bibles do not have God’s name clearly translated, but have “Lord” where the Hebrew has Yahweh. This confuses many Christians who see “Lord” in both the Old and New Testaments, and assume it is the same person. Also, many Christians who have some training in the Scriptures have been taught that Yahweh in the Old Testament was Jesus Christ. So, instead of seeing Yahweh in Joel and “Lord” in Romans, and then realizing that the Lord Jesus is now doing what Yahweh did, they erroneously believe the same person is acting in both places.
God made Jesus Lord and gave him all authority. This verse and others show that Jesus has taken on many of the jobs God used to do. We understand that perfectly in our culture, because we know what it means to get a promotion and take over a job someone else used to do. With the promotion and new job often comes a new title. Thus, “this same Jesus” was made “Lord” and “Christ” and was given all authority, including raising the dead and judging the people (John 5:21-27). The verses in the Old Testament that speak of God’s authority are often quoted in the New Testament and applied to Christ because God gave the authority to Christ.
Snedeker, pp. 403-406