Adam Clarke on Matthew 10:17

But beware of men - Or, be on your guard against men, των ανθρωπων These men; i.e. your countrymen; those from whom you might have reasonably expected comfort and support; and especially those in power, who will abuse that power to oppress you.

Councils - Συνεδρια, sanhedrins and synagogues. See on Mat 5:22 (note). "By synagogues we may understand here, not the places of public worship, but assemblies where three magistrates, chosen out of the principal members of the synagogue, presided to adjust differences among the people: these had power, in certain cases, to condemn to the scourge, but not to death. See Act 22:19; 2Cor 11:24, compared with Luk 12:11." See Lightfoot.