Thomas Aquinas

Paul and Sylvanus and Timothy
He, in writing to these good people, does not mention his title, but supplies only his humble name which is Paul. He also adds the names of two persons who preached to them with him: Silvanus, who is Silas, and Timothy, whom he circumcised, as is mentioned in Acts 16. Paul greets the church, which is the assembly of believers,

in God our Father and the Lord Jesus Christ,
that is, in the faith of the Trinity and of the divinity and humanity of Christ, because our beatitude will consist in knowing them. He mentions only the person of the Father and the incarnate Son, in which two is understood the Holy Spirit who is the bond between the Father and the Son.

The blessings he asks are grace, which is the source of all good things: “But by the grace of God I am what I am” (I Cor. 15: 10); and peace, which is our end: for there is peace when desire is totally at rest.

'we ought to give thanks,'
Paul mentions things that ought to be present in thanksgiving. First, thanksgiving should be directed to God:

we give thanks always to God.
“He bestows favor and honor” (Ps. 84:11). “Every good endowment and every perfect gift is from above, coming down from the Father of lights” (Jas. 1: 17). Thanksgiving should be unceasing; so Paul says, always.

all the wicked who have gone before are signs of the Antichrist.

To quote the words of Augustine (De Civ. Dei xx, 19), "it is a matter of debate whether they are called signs and lying wonders, because he will deceive the senses of mortals by imaginary visions, in that he will seem to do what he does not, or because, though they be real wonders, they will seduce into falsehood them that believe." They are said to be real, because the things themselves will be real, just as Pharaoh's magicians made real frogs and real serpents; but they will not be real miracles, because they will be done by the power of natural causes, as stated in the; whereas the working of miracles which is ascribed to a gratuitous grace, is done by God's power for man's profit.

The Apostles, led by the inward instinct of the Holy Spirit, handed down to the churches certain instructions which they did not put in writing, but which have been ordained, in accordance with the observance of the Church as practiced by the faithful as time went on.