Part of the expression of his being for us is that he is with us. "Being for" always takes expression in some form of "Being with." If we are for a particular political candidate, we are with them by voting for them. When we purchase a certain product we are for, we show that we are with it. (That may be strectching it a bit, but you get the idea.)
God demonstrated he was for his people by being with them in several ways. He was with them in the wilderness for 40 years after they came out of Egypt. He showed his "with-ness" with a pillar of fire and a pillar of smoke. God commanded construction of the Ark of the Covenant and the temple as pictures of
God with his people had practical, as opposed to symbolic, effects also. God showed he was with Israel when he sent plagues to Egypt. Manna (physical provision in the wilderness) and parting the Read Sea are marks of "with-ness." The roller coaster ride of Judges (Israel's apostasy, leading to judgment, leading to oppression from other countries, leading to Israel's repentance, leading to God's rescue and restoration) shows that God is with his people, even after they continually turned their backs on him.