Acts 8:37-38

‘And he commanded the chariot to stand still. And they both went down into the water, both Philip and the eunuch, and he baptised him.'

Knowing that God had specifically sent him here, and seeing and hearing the man's response, Philip could see no objection. So the conveyance was brought to a halt, and climbing down they went into the water and Philip baptised the eunuch. Here it is made quite clear that baptism has to be performed by a baptiser. This is never so in Jewish ritual cleansings, demonstrating that this is not a ritual cleansing but a portrayal of the pouring out like rain of the Holy Spirit in rivers bringing life and fruitfulness (see note on Acts 22:16).