Jamieson, Fausset and Brown on 2 Samuel 4:7

7. when they came into the house, he lay on his bed--Rechab and Baanah came in the heat of the day, when they knew that Ish-bosheth, their master, would be resting on his divan; and as it was necessary, for the reason just given, to have the corn the day before it was needed, their coming at that time, though it might be a little earlier than usual, created no suspicion, and attracted no notice [Harmer].

gat them away through the plain--that is, the valley of the Jordan, through which their way lay from Mahanaim to Hebron.