What place is it of man to declare someone a “Saint”?
Come, rejoice with us in God's abundant mercy!
The practice of recognizing saints dates back to the 1st century. It is based on scripture. The Bible directs us to invoke those in heaven and ask them to pray with us. Thus in Psalms 103, we pray, "Bless the Lord, O you his angels, you mighty ones who do his word, hearkening to the voice of his word! Bless the Lord, all his hosts, his ministers that do his will!" (Ps. 103:20-21). And in Psalms 148 we pray, "Praise the Lord! Praise the Lord from the heavens, praise him in the heights! Praise him, all his angels, praise him, all his host!" (Ps. 148:1-2).
Not only do those in heaven pray with us, they also pray for us. In the book of Revelation, we read: "[An] angel came and stood at the altar [in heaven] with a golden censer; and he was given much incense to mingle with the prayers of all the saints upon the golden altar before the throne; and the smoke of the incense rose with the prayers of the saints from the hand of the angel before God" (Rev. 8:3-4).
And those in heaven who offer to God our prayers aren’t just angels, but humans as well. John sees that "the twenty-four elders [the leaders of the people of God in heaven] fell down before the Lamb, each holding a harp, and with golden bowls full of incense, which are the prayers of the saints" (Rev. 5:8). The simple fact is, as this passage shows: The saints in heaven offer to God the prayers of the saints on earth.
We see examples of this in the Old Testament as well. In Tobit 12:12,15 - angels place Tobit and Sarah's prayers before the Holy One. This teaches us that the angels are also our subordinate mediators. We pray to the angels to take up our prayers to God. And, in 2 Macc. 15:12-16 – the high priest Onias and the prophet Jeremiah were deceased for centuries, and yet interact with the living Judas Maccabeas and pray for the holy people on earth.
For the same reason that man (Peter) and his successors were given full authority by Christ to declare things bound and unbound on earth and the decision would be acceptable in heaven.
He has not been declared a saint. That may happen, or not, sometime in the future. A beatification is a step on the road to sainthood, but not the final step.