Acts 2:37

Acts 2:37-38 (see also Ephesians 1:13)
Now when they heard this, they were pierced to the heart, and said to Peter and the rest of the apostles, “Brethren, what shall we do?” Peter said to them, “Repent, and each of you be baptized in the name of Jesus Christ for the forgiveness of your sins; and you will receive the gift of the Holy Spirit.”

One thing that makes this passage particularly troublesome for Calvinism is the fact that the promise of forgiveness was indiscriminately held out to each of you,” instead of being exclusively held out to only those of the Calvinistically elect, for whom Jesus (allegedly) alone had died to save and efficaciously secure the promise of redemption through repentance. In other words, if there was a person in the audience who was not of the alleged, Calvinistically elect, then they would have no Savior, for which their repentance could be received. By randomly telling someone to repent, you are holding out the hope that their repentance can have a beneficial result. But if they are not of the Calvinistically elect, then any hypothetical repentance would be in vain. Therefore, it is reasonable to conclude that Peter’s perspective of indiscriminately holding out the hope of salvation, reveals an Arminian mindset.