Ancient Literary sources about ancient Macedonian language being a Greek dialect

1.

Quote:

[3] When day dawned and the inhabitants had realized the danger that beset them, they were at first under the impression that the Lacedaemonians had forced an entry into the town, and attacked them more recklessly owing to their ancient hatred. But when they discovered from their equipment and speech that it was the Macedonians and Demetrius the son of Philip, they were filled with great fear, when they considered the Macedonian training in warfare and the good fortune which they saw that they enjoyed in all their ventures.

[Pausanias Messeniaka XXIX, 3]

This quote shows Messenians were able to understand Macedonian speech, thus they recognized the newcomers were Macedonians and Demetrius, son of Philip.

2.

Quote:

But some go so far as to call the whole of the country Macedonia, as far as Corcyra, at the same time stating as their reason that in tonsure, language, short cloak, and other things of the kind, the usages of the inhabitants are similar

[Strabo 7.7.8]

Interestingly we learn from this quote Macedonians spoke similar language to the Greeks “as far as Corcyra”. We know Epirotes spoke a North-West Greek so obviously the North-West Greek dialect was also spoken by Macedonians.

3.

Quote:

But while he lay encamped there near him, many who came out of Beroea infinitely praised Pyrrhus as invincible in arms, a glorious warrior, who treated those he had taken kindly and humanely. Several of these Pyrrhus himself sent privately, pretending to be Macedonians, and saying, now was the time to be delivered from the severe government of Demetrius, by coming over to Pyrrhus, a gracious prince, and a lover of soldiers.

[Plutarch Pyrrhus XI.4]

So Pyrrhus planted some of his Epirotes into Macedonian army urging Macedonians to get rid of Demetrius since Epirotes spoke the same Greek dialect as Macedonians.

4.

Quote:

one recollecting himself, stripped off a piece of bark from an oak, and wrote on it with the tongue of a buckle, stating the necessities and the fortunes of the child, and then rolling it about a stone, which was made use of to give force to the motion, threw it over to the other side, or, as some say, fastened it to the end of a javelin, and darted it over. When the men on the other shore read what was on the bark, and saw how time pressed, without delay they cut down some trees, and lashing them together, came over to them. And it so fell out, that he who first got ashore, and took Pyrrhus in his arms, was named Achilles, the rest being helped over by others as they came to hand.

[Plutarch Pyrrhus II.1]

Plutarch tells us the story of the infant Pyrrhus when his companions tried to save the infant Pyrrhus from Molossians and while heading to the court Of Glaucias, they came across Megara, a Macedonian village in the other side of where they were. Apparently the Macedonian peasants were able to read the message of the Epirotes guards of Pyrrhus since they spoke the same language thus they helped them.

5.

Quote:

Alexander speaks: “The Macedonians are going to judge your case,” he said. “Please state whether you will use your native language before them.”Philotas: “Besides the Macedonians, there are many present who, I think, will find what I am going to say easier to understand if I use the language you yourself have been using, your purpose, I believe, being only to enable more people to understand you.”

Curtius VII 9.25 – 11.7

in fact in Philotas affair it becomes even clearer Macedonian is a Greek dialect, since Philotas explicitely states that using the Koine would make his speech “easier to understand“, indicating that Macedonian dialect was not incomprehensible to the non-Macedonians, but a bit more difficult to understand. In fact, the whole incident shows the Macedonian dialect was not that different from the Koine and could be understood eventhough it had some difficulty by other Greeks. This also explains the quick disappearance of the Macedonian dialect and the quick adoption of the Koine from Macedonians.

6.

Quote:

Aetolians, Acarnanians, Macedonians, men of the same language

[T. Livius XXXI,29, 15]

Nothing more to be added. Aetolians, Acarnanians and Macedonians spoke the same language.

7.

Quote:

“General Paulus of Rome surrounded by the ten Commissioners took his official seat surrounded by the whole crowds of Macedonians…Paulus announced in Latin the decisions of the Senate, as well as his own, made by the advice of his council. This announcement was translated into Greek and repeated by Gnaeus Octavius the Praetor-for he too was present.

[T. Livius, XLV]

Another proof the Macedonian population spoke Greek.

8.

Quote:

“In pursuit of Bessus the Macedonians had arrived at a small town inhabited by the Branchidae who, on the orders of Xerxes, when he was returning from Greece, had emigrated from Miletus and settled in this spot. This was necessary because, to please Xerxes, they had violated the temple called the Didymeon. The culture of their forebears had not yet disappeared thought they were now bilingual and the foreign tongue was gradually eroding their own. So it was with great joy that they welcomed Alexander, to whom they surrendered themselves and their city. Alexander called a meeting of the Milesians in his force, for the Milesians bore a long-standing grudge against the Branchidae as a clan. Since they were the people betrayed by the Branchidae, Alexander let them decide freely on their case, asking if they preferred to remember their injury or their common origins. But when there was a difference of opinion over this, he declared that he would himself consider the best course of action.When the Branchidae met him the next day, he told them to accompany him. On reaching the city, he himself entered through the gate with a unit of light-armed troops. The phalanx had been ordered to surround the city walls and, when the signal was given, to sack this city which provided refuge for traitors, killing the inhabitants to a man. The Branchidae, who were unarmed, were butchered throughout the city, and neither community of language nor the olive-branches and entreaties of the suppliants could curb the savagery. Finally the Macedonians dug down to the foundations of the city walls in order to demolish them and leave not a single trace of the city.”

[Curtius VII.5.29]

The greek-speaking Branchidae had common language with Macedonians.