Radak: This is like "Hashem Necheni b'Tzidkasecha" (Tehilim 5:9). I.e. He will always supervise over you, wherever you turn. Malbim - you will not need to call to Him. He will guide you without ceasing for a moment.

Rashi citing Targum Yonasan: At a time of thirst and famine.

Radak: It is dryness, like "Tzachah Tzama" (5:13). When you will be thirsty and lacking good in the world, He will satiate your Nefesh.

Malbim: Your spiritual happiness will be great. He will satiate your Nefesh with clear light.

Rashi: It is to arm, like "Chalutzei Tzava" (Bamidbar 31:5).

Radak #1: he will fatten them. This is like "Shemu'ah Tovah Tedashen Etzem" (Mishlei 15:30). It mentions the bones, for they are the foundation of the body. Chazal said, the Shali'ach Tzibur on Rosh Hashanah says 'Hachalitzenu' - satiate us and fatten us with Your Mitzvos.

Radak #2: Give to us rest. This word has four meanings - removal ("v'Chaltzah Na'alo" - Devarim 25:9), saving ("Chaltzeni Hashem" - Tehilim 140:2), arming ("Ya'avru Chalutzim" - Bamidbar 32:30), and giving rest (v'Atzmosecha Yachalitz). This is like we say (in Birkas ha'Mazon on Shabbos) 'Retze v'Hachalitzenu.'

Malbim: This refers to bodily perfection. He will make your bones strong, fresh and youthful.

Radak: Springs water it, and it is always satiated. Its vegetables are moist.

Malbim: The moisture of the roots fills everything that sprouts in it

Radak: It flows even at a time of dryness. Chazav is the end of a matter, as if it lies, and it never was, like "Kichesh Ma'ase Zayis" (Chabakuk 3:17).

Malbim: This refers to spiritual success. It is like a water source from which people draw water with Simchah; you will spread your Chachmah to many.