Jamieson, Fausset & Brown

For if we have been planted together--literally, "have become formed together." (The word is used here only). in the likeness of his death, we shall be also in the likeness of his resurrection--that is, "Since Christ's death and resurrection are inseparable in their efficacy, union with Him in the one carries with it participation in the other, for privilege and for duty alike." The future tense is used of participation in His resurrection, because this is but partially realized in the present state. (See on Rom 5:19).