"If you walk in My statues and keep My commandments, and perform them, then I will..." (Leviticus 26:3-4; NKJV).
"If" is a conditional clause. "If" the people would cultivate a lifestyle of obedience to the statues and commandments of Jehovah, "then" He would bless them. "If" they failed to obey, "then" Jehovah would set His "face against" them (Leviticus 26:14, 17; NKJV).
Consider these words of Jesus: "If you love me, keep My commandments" (John 14:15; NKJV).
Jason Cicero