יְצַ֨ו יְהוָ֤ה אִתְּךָ֙ אֶת־הַבְּרָכָ֔ה בַּאֲסָמֶ֕יךָ וּבְכֹ֖ל מִשְׁלַ֣ח יָדֶ֑ךָ וּבֵ֣רַכְךָ֔ בָּאָ֕רֶץ אֲשֶׁר־יְהוָ֥ה אֱלֹהֶ֖יךָ נֹתֵ֥ן לָֽךְ׃
L’Éternel fixera chez toi la bénédiction, dans tes celliers, dans tous tes biens; il te rendra heureux dans ce pays que l’Éternel, ton Dieu, te destine.
Ibn Ezra
The context of the word warehouses indicates that it must mean “storehouses”, or something similar.
Kli Yakar
The Lord will command the blessing [to be] with you in your storehouses. Since it is said You will decree a thing, and it will be established for you (Job 22:28). When a righteous person decrees something, the Holy One, blessed be He, agrees with him, as in Sun, stand still at Gibeon (Joshua 10:12), and like Elijah who said, The jar of flour shall not be used up (1 Kings 17:14), and in the Tractate Taanit (25a) regarding Rabbi Chanina ben Dosa, “Let your beams reach,” and many similar cases. Therefore it says, The Lord will command the blessing to be with you, meaning when you command blessing, then God will command along with you and will concur with your blessing and your command.
Rashbam
באסמיך, in your storage chambers which will be bursting full with different kinds of grain, grapes, and olives. This is described graphically in Proverbs 3,10 וימלאו אסמיך שבע,”and your barns will be filled with food, your vats will burst with new wine.”