Here is the Harmony of the Gospels in the Aquinas Study Bible
The Women at the Tomb
(Matt 28:1-8 Mark 16:1-8 Luke 24:1-12 John 20:1-13)
Mary Magdalene and the other Mary. (Mt 28:1) That is, the wife of Cleophas and mother of James. These were the leaders and standard-bearers of the rest who were wont to follow Christ; for that there were several others is clear from Luke 23:55, where, among others, he names Joanna, the wife of Chuza, Herod’s steward: and Mark adds Salome. (Mark 16:1) The Blessed Virgin Mother of God did not come with them, because she certainly knew and expected that Christ would rise on that same day; whence she knew that the anointing would be useless.
You will say, How do Matthew and Mark say that the angel sat, (Mt 28:5 Mark 16:5) when Luke says that he stood? (Luke 24:4) I answer, that by a Hebraism, to stand is a term applicable to any position; for it only signifies that a thing is present, whether standing upright, or sitting, or lying. Then, also, the account given by Matthew and Mark is a different one from that given by Luke, as I shall presently show.
You will say, secondly, How does Matthew say that the angel sat upon the stone rolled back, that is, outside the sepulchre, (28:2) when Mark says that the women saw the angel not outside,(Mark 16:5) but on entering into the tomb? I answer, that the angel first removed the stone which closed the sepulchre, and then terrified the watch who were outside, and drove them away, so that they might not hinder the women from approaching the sepulchre; then, that he entered the sepulchre itself, and was there seen by the women, that he might show them the empty sepulchre, and that Christ had risen. Whence he says, “He is risen, as He said; come, see the place where the Lord lay.” (Mt 28:6 Mark 16:6) So Theophylact. Or, rather, the angel of whom Matthew speaks was a different one from that of whom Mark speaks. So Barradius.
But I maintain that the same angel is spoken of by Mark as by Matthew. For Mark is generally the interpreter of Matthew. Wherefore, what Mark says about their entering into the tomb is to be understand thus, when they were preparing or beginning to enter the tomb; for they had not yet entered it, but were still outside, and there they saw and heard the angel, as Matthew has it. For to enter signifies, here and elsewhere, an act begun and not finished.
And the angel answered, &c. (Mt 28:5) You will say, How is it that Matthew and Mark speak only of one angel as seen by the women, when Luke affirms that two were seen, who comforted the women with different words from those which Matthew and Mark have? I answer that the account of Luke (24:4) is different from that of Matthew, and that he relates what happened later, as I shall hereafter show. The women. Namely, the Magdalene, Mary the mother of James, Joanna, and the rest (see Luke 24:10). Those are mistaken, therefore, who think that Magdalene, after she had seen the empty sepulchre, immediately ran back to tell the Apostles, without seeing the angels, and that they were only seen by Mary the mother of James and the rest. John, therefore (Jn 20:1), while he mentions Magdalene only, with her understands all the rest of her companions; for she was the leader and chief of them all.
In the historical order of the events must be brought in here what Luke mentions (24:3), namely, that Magdalene and her companions, while at the invitation of the angel they had entered the sepulchre and seen that it was empty, yet were affrighted; on account of which the angels cheered them, and at the same time gently reproved their want of faith. For that Luke’s account is not the same as that of Matthew and Mark, as some think, is clear from the words themselves, which are evidently different. Also, from the circumstance that in Luke two angels are said to have appeared, while in Matthew and Mark only one is mentioned.
Tell His disciples. (Mt 28:7) Matthew does not mention what they told; but John and Luke explain it, but in different ways. For John says that Magdalene only said to Peter,(Jn 20:2) They have taken away my Lord out of the sepulchre, and we know not where they have laid Him. But Luke says that they related to the Apostles all the things they had seen and heard. (Luke 24:10)
You will say, Whence this difference? I answer, It arises from the women being possessed with fear and doubt, and therefore they told no one anything by the way. And because they did not firmly and certainly believe that Christ had risen, they spoke alternating words, in accordance with the alternations of their thoughts; for at one time they speak of the vision of angels, at another they declare their opinion that the body of the Lord had been taken away.
At this point we must bring into the history what S. John relates (Jn 20:2-19).
Magdalene, then, was the first to see Christ, as Mark says. Afterwards, at the command of Christ, she hastened after the other women, and overtook them, and then with them again saw Christ, and heard His salutation. So St. Chrysostom, St. Jerome, and others. (Cornelius a Lapide)
Once I read Matthew, Luke, Mark, John and Acts thoroughly, a couple things became obvious: