In covenant settings, to love often means "to choose." The Lord truly loves his people. But in this context, it means that he chose them as his special possession (4:20).
Your hand: This phrase uses a picture to show safety. It means that Israel, called his holy ones, was secure in the Lord’s care.
his steps: To follow the Lord means "to live as he teaches and to go where he leads." It describes a way of life that matches his ways.
Your words: This refers especially to the Torah. The Torah is the law that God gave to Israel. It includes all of his instructions for their life together.