There is a distinction between an incentive for the individual to perform a commandment, (as in this case), and God's stated reason why an act should be done. Both are found elsewhere. Example of the former: Deuteronomy (22:7) which relates to sending away the mother bird:
Thou shalt in any wise let the dam go, but the young thou mayest take unto thyself; that it may be well with thee, and that thou mayest prolong thy days. (Trans. JPS)
Additionally, there are associations between general mitzvah observance, and reward, e.g. Deut. (4:1), (5:30), (6:2), (6:18), (8:1), and (11:8).
Example of the latter: Exodus (13:9); the mitzvah of tefillin:
And it should be a sign on your arm for you, and as a remembrance between your eyes, so that the law of God will be in your mouth. (Trans. my own).
Additionally, note Leviticus (23:43-4); the mitzvah of sitting in sukkot:
Ye shall dwell in booths seven days; all that are home-born in Israel shall dwell in booths; so that your generations may know that I made the children of Israel to dwell in booths, when I brought them out of the land of Egypt: I am the LORD your God. (Based on JPS).
Also, Numbers (15:39-40); the mitzvah of tsitsit:
And it shall be unto you for a fringe, that ye may look upon it, and remember all the commandments of the LORD, and do them; and that ye go not about after your own heart and your own eyes, after which ye use to go astray; so that ye may remember and do all My commandments, and be holy unto your God. (Based on JPS).
Sometimes the nature of a reason; i.e. whether it is an incentive or the very reason for the command, or both, may not be self evident. E.g. Exodus (23:12); the mitzvah of Shabbat:
Six days thou shalt do thy work, but on the seventh day thou shalt rest; so that thine ox and thine ass may have rest, and the son of thy handmaid, and the stranger, may be refreshed. (Based on JPS).
Cf. Deut. (5:14).