Worship Elements: Sacraments General (Romans 4:11)

The Apostle Paul speaks Abraham first having faith and then receiving he sign. This would seem that the sacraments are a sign of our faith rather than a sign of the covenant.  This has profound implications because this would mean that first we would profess our faith and then receive the sacrament.  So, why would we as reformed people baptize infants if this contradicts the Apostle Paul? Why would infants potentially receive the sign if they have not first professed faith like Abraham did?