This comes after they lost a vote on contempt in parliament yesterday
It was all about the contempt vote yesterday more than the debate about the Brexit deal and May's government lost out on the vote there - seen as a preview of the meaningful vote next week.
As mentioned yesterday, the challenge on contempt is more of a sentiment gauge but also serves to destabilise May over the next few days of debate ahead of next Tuesday's vote.
Update: The Telegraph now reports that parliament leader Andrea Leadsom says the advice will be published at 1100 GMT. The headline above is by Bloomberg so it's a bit conflicting but in general look out for it between 1100 to 1130 GMT.