Household and Infant baptism.
Reformed churches baptise children, not because we believe there is any grace in the sacrament as Roman Catholics do, but “because baptism is a covenant sign (Col.2:11-12) and, since the children of believers are included in the covenant (Gen.17:7), the sign of the covenant must also be administered to them. When we say it is a covenant sign, we mean that it takes the place of circumcision as the symbol of God’s saving grace to believers and their children.” Abraham is commanded to administer the sign to all his house (males) and given the promise God would gather his elect from among his children. “As a sign, circumcision represented a spiritual circumcision of the heart (Rom.2:28-29) in which the body of sin is put off….the same thing that baptism represents–regeneration and the washing away of sin.” What baptism represents may occur retrospectively or prospectively, in other words, an elect infant may already be regenerate, as were John the Baptist and Jeremiah, or may become so, much later in life.
Baptism “is a symbol of God’s grace and promise to believers and their elect children (Acts 2:39).” Neglecting to administer the covenant sign to our children is despising God’s covenant and promises.
As to the mode, one verse settles it for me, namely I Corinthians 12:13 “For by one Spirit are we all baptized into one body, whether we be Jews or Gentiles, whether we be bond or free; and have been all made to drink into one Spirit.” Spirit baptism is the reality symbolised by water baptism (not primarily death and resurrection as Baptists say) and clearly we are born again from above as the Spirit is poured out upon us (and incidentally also cleansed by the sprinkling of the blood of Christ as per I Peter 1:2).
Quotes come from article in Standard Bearer June 2015 by Rev. Rodney Kleyn.