Christ’s first words in the first Gospel are “Suffer (aphiemi) it be so now, for thus it is fitting to fulfil all righteousness (Mt. 3:15)”. These first words of the Word are followed by his baptism, the opening of the heavens, and the first public manifestation of the Trinity: with the Son first making himself present in word, the Holy Spirit making himself present as a dove, and the Father making himself present by his voice “this is my Beloved Son…”
The first word of Christ “Suffer it be…” is meant in the sense of “allow it to be” but the word “suffer” is the same word used by Christ when he foretells his passion “The Son of Man must suffer many things…be rejected by the Priests, be slain.. (Lk, 9:22)” And so we can see Christ’s first words as both showing us the Trinity, and making explicit reference to his passion. The Catholic and the Orthodox draw these two things together at the beginning of every prayer by making the sign of the cross, where one invokes the name of the Trinity in the four points of the cross.