A.T. Robertson Commentary Acts 4:21

"And they, when they had further threatened them, let them go, finding nothing how they might punish them, because of the people; for all men glorified God for that which was done." — Acts 4:21 (ASV)

When they had further threatened them (προσαπειλησαμενο). The "further" is in "pros" (in addition),

Finding nothing how they might punish them (μηδεν ευρισκοντες το πως κολασωντα αυτους). Note the article "to" before πως (how), "the how." Aorist middle deliberative subjunctive κολασωντα in indirect question after πως from κολαζω, to lop (κολος, lopped), to curb, to prune, to correct, to punish. Old verb, in the N.T. only here and 2 Peter 2:9.

Glorified God (εδοξαζον τον θεον). Imperfect active, kept on glorifying God while the Sanhedrin were threatening Peter and John. It was to laugh at the helplessness of the Sanhedrin.