Acts 9:13

Then Ananias answered, Lord
Though Ananias knew that it was the Lord that spoke, and acknowledged his power and dominion, and expressed his readiness to obey his commands; yet there was a timidity in him, and which was the more inexcusable, that it should appear after the Lord had told him of the vision which Saul had had of him; and yet still he was fearful of putting himself into his hands, who had been so violent a persecutor; and therefore obliquely excuses himself, by observing what Saul had done at Jerusalem, and the powers he came with to Damascus:

I have heard by many of this man;
which shows that Ananias had been at Damascus some time, and was not an eyewitness of the havoc Saul made of the church, only had the account of it from others; and these many who fled to Damascus upon the persecution, which Saul was at the head of; and being so, was particularly spoken of, and his name was well known, and was become infamous for his cruelty and barbarity;

how much evil he hath done to thy saints at Jerusalem;
by entering into their houses with violence, haling men and women from thence, committing them to prison, and persecuting them unto death. Believers in Christ are called his "saints", because separated by his grace for his service, and sanctified by his Spirit, and to whom he is made sanctification; and because they live holy lives and conversations; all which is an aggravation of the evil done them, and which will be avenged by Christ in his own time.