Thou art mad (mainēi). Present middle indicative second person singular. Old verb, only in the middle voice. Festus used the same word to Paul (Act 26:24). The maid was undoubtedly excited, but it was a curious rebuff from those who had been praying all night for Peter’s release. In their defence it may be said that Stephen and James had been put to death and many others by Saul’s persecution.
She confidently affirmed (diischurizeto). Imperfect middle of diischurizomai, an old word of vigorous and confident assertion, originally to lean upon. Only here in the N.T. The girl stuck to her statement.
It is his angel (Ho aggelos estin autou). This was the second alternative of the disciples. It was a popular Jewish belief that each man had a guardian angel. Luke takes no position about it. No scripture teaches it.