‘And Jael went out to meet Sisera, and said to him, ‘Turn in, my lord, turn in to me. Do not be afraid.'
Jael went out to meet him. She would see the hunted look of the fugitive and realise what had happened. She would also know how important a man he was for the wellbeing of the Canaanites. It may be that she knew that he was making for Hazor and determined to prevent him reaching there by a ruse. But it may be that she had some private reason for revenge. There is much about the narrative, including its silences, to suggest so. But the writer is not interested in her private revenge, only in the fulfilment of Deborah's prophecy. And he is enjoying what happened.
So she offered him refuge, but in a forbidden place, in a woman's tent, the tent of his ally's wife, alone. This was a breach of etiquette of the highest level, especially between men who had some kind of covenant between them. A nobler and less terrified man would have refused. He must have known what her husband's view would be. What the view of all good men would be. And it would be disastrous for her reputation for him to be alone with her. The truth is that ‘Turn in to me' was possibly seen by him as an invitation to enjoy more than just food and drink, otherwise he would surely have protested, which makes his behaviour even more despicable. What protection did he deserve when he behaved like this? But he was used to being welcomed by women. He would make use of her in two ways at the same time. He may well have made the attempt before.
“My lord.” A polite address to an important man. But she would call her husband ‘my lord' as well.
‘And he turned in to her into the tent; and she covered him with a covering.'
This was possibly in order to hide him, but more likely it was because he stripped some of his ‘armour' off. It was heavy and uncomfortable and he was very hot, very tired, and felt safe. The covering or rug (some kind of covering - the word occurs only here and its specific meaning is not known) was to preserve some level of propriety. But how could that be in a married woman's tent? It accentuates the position.