Albert Barnes on Mark 12:40

Which devour widows' houses. Which devour the families of widows, or the means of supporting their families. This they did under pretence of counselling them in the knowledge of the law, and in the management of their estates. They took advantage of their ignorance and unprotected state, and either extorted large sums for their counsel, or perverted the property to their own use. No wonder that our Saviour denounced them! If there is any sin of peculiar enormity, it is thus taking advantage of the circumstances of the poor, the needy, and the helpless, and wronging them out of the pittance on which they depend to support their families. And as God is the Friend of the widow and the fatherless, it may be expected that such will be visited with heavy condemnation.

For a pretence. For show, or pretending great devotion.

(v) "widow's houses" 2Ti 3:6