Mysia - This was a province of Asia Minor, having Propontis on the north, Bithynia on the east, Lydia on the south, and the Aegean Sea on the west.
They assayed - They endeavored; they attempted.
Into Bithynia - A province of Asia Minor lying east of Mysia.

After they were come to Mysia - They passed through Phrygia into Mysia, which lay between Bithynia on the north, Phrygia on the east, Aeolia on the south, and the Mediterranean on the west.
But the Spirit suffered them not - God saw that that was not the most proper time to preach the word at Bithynia; as he willed them to go immediately to Macedonia, the people there being ripe for the word of life. Instead of το πνευμα, the Spirit merely, το πνευμα Ιησου, the Spirit of Jesus, is the reading of ABCDE, several others, with both the Syriac, the Coptic, Ethiopic, Armenian, Vulgate, Itala, and several of the fathers. The reading is undoubtedly genuine, and should be immediately restored to the text.

After they were come to Mysia,.... Another country in Asia Minor. It is divided by Ptolomy (a) into two parts; superior Mysia is bounded by Dalmatia on the west, by Macedonia on the south, by part of Thrace on the east, and by part of the river Danube on the north; inferior Mysia is bounded on the west with part of the river Ciaber and the Danube, on the south with part of Thrace, on the north with the turn of the river Tyra, and on the east with the Euxine Pontus; but this was the European Mysia: the Mysia which seems here intended, was divided into the lesser Mysia by the Hellespont, and had Troas on the south; and into the greater Mysia by Olympus, which was bounded on the west with the lesser Mysia and Troas, on the east with Bithynia, and on the south with Asia, properly so called. By Pliny (b) it is called Aeolis, and so Jerom says (c), it was in his times; sometimes it is called Abretta and Abrettina, and of later years Thya, or Thyria: some suggest it has its name of Mysia from Mysus, the brother of Car (d), the father of the Carions; but according to the Talmudists, it had its name from Meshech, the son of Japheth, Genesis 10:2 for they say (e) Meshech, , "this is Mysia"; Pliny observes (f), that there are some authors who assert that the Mysians, Brygians, and Thynnians came out of Europe, from whom they are called Mysians, Phrygians, and Bithynians, in Asia. The inhabitants of Mysia were very despicable; hence the proverb, "ultimus Mysorum", "the last of the Mysians" (g), is used for a very mean and contemptible person. The apostle was willing to preach to the wise and unwise, and disdained not to carry the Gospel to the meanest part of mankind.
They assayed to go into Bithynia; another country in Asia Minor; it makes one province with Pontus, and has the same boundaries; Pontus being at the east, and Bithynia at the west: it was bounded on the north with the Euxine sea, on the east with Galatia, on the south with Asia properly so called, and on the west with the Propontis; according to Pliny (h) it was called Cronia, afterwards Thessalis, then Maliande, (perhaps Mariandyne), and Strymonis; and Herodotus (i) reports, that the Thracians going into Asia were called Bithynians, who were first called (as they say) Strymonians, inhabiting Strymon; according to Jerom (k), it was formerly called Bebrycia, then Mygdonia, and Phrygia Major, and by the river Iera, or, as Pliny calls it, Hieras, is divided from Galatia; to which agrees Solinus (l) who says it was before Bebrycia, afterwards Migdonia, and now Bithynia, from Bithynus the king; the king; though others say, it was so called from Bithyne, a daughter of Jupiter;
but the Spirit suffered them not; the Alexandrian copy, and Beza's most ancient copy, and some others, and the Vulgate Latin, Syriac, and Ethiopic versions read, "the Spirit of Jesus": so that it was not an evil spirit, or Satan, that hindered them, who sometimes did; but they were under the direction and guidance of the divine Spirit, called, in the preceding verse, the Holy Ghost; however, the Gospel was preached here afterwards, and churches formed; of which See Gill on 1-Peter 1:1.
(a) Geograph. l. 3. c. 9, 10. (b) Nat. Hist. l. 5. c. 30. (c) De locis Hebraicis, fol. 96. E. (d) Herodotus, l. 1. c. 171. (e) T. Bab. Yoma, fol. 10. 1. (f) Nat. Hist. l. 5. c. 32. (g) Ciceron. Orat. 24. pro. L. Flacco, p. 785. (h) Ib. (i) Polymnia, c. 75. (k) De locis Hebraicis, fol. 95. L. (l) Polyhistor. c. 54.

After they were come to Mysia--where, as being part of Roman Asia, they were forbidden to labor (Acts 16:8).
they assayed--or attempted
to go into--or, towards.
Bithynia--to the northeast.
but the Spirit--speaking as before.
suffered them not--probably because, (1) Europe was ripe for the labors of this missionary party; and (2) other instruments were to be honored to establish the Gospel in the eastern regions of Asia Minor, especially the apostle Peter (see 1-Peter 1:1). By the end of the first century, as testified by PLINY the governor, Bithynia was filled with Christians. "This is the first time that the Holy Ghost is expressly spoken of as determining the course they were to follow in their efforts to evangelize the nations, and it was evidently designed to show that whereas hitherto the diffusion of the Gospel had been carried on in unbroken course, connected by natural points of junction, it was now to take a leap to which it could not be impelled but by an immediate and independent operation of the Spirit; and though primarily, this intimation of the Spirit was only negative, and referred but to the immediate neighborhood, we may certainly conclude that Paul took it for a sign that a new epoch was now to commence in his apostolic labors" [BAUMGARTEN].

Coming to Mysia, and passing it by, as being a part of Asia, they attempted to go into Bithynia; but the Spirit suffered them not - Forbidding them as before. Sometimes a strong impression, for which we are not able to give any account, is not altogether to be despised.