‘But having suffered before, and been shamefully treated, as you know, at Philippi, we waxed bold in our God to speak to you the Gospel of God in much conflict.'
The second evidence of his genuineness is that he was willing to go on preaching even though it brought him much suffering. They knew how badly treated he had been at Philippi (Acts 16:12-40), but this had not prevented them from coming to Thessalonika, and continuing to preach boldly even though there were the signs of the same things happening to him there (Acts 17:5). He had not flinched or hesitated. He had been willing to suffer among them for the Gospel's sake while proclaiming that ‘Good News from God' to them. Note the stress that the Good News they had brought was ‘of God'. It was God's Good News, not his.
‘Shamefully treated', that is treated arrogantly or spitefully. At Philippi the law was called in and false accusations were made against them. They were then scourged and put in the stocks in prison.
‘Waxed bold', that is had the courage to speak freely. Did not hold anything back for fear of misinterpretation. And this was because they knew that they were ‘in our God', Who watched over them and protected them, for it was His good News that they proclaimed.
‘Much conflict.' This probably refers to external conflict rather than inner conflict. The Thessalonian opponents also called in the law. It was a time of great upheaval and coping with strong opposition.