9 refers to judgement, completeness from God, the fruit of the Spirit. 9 also refers to natural processes: as we all know, it takes 9 months for a a child to grow in the mothers womb. It signifies 3 perfect manefestations of 3 plans (3x3): body/matter, spirit, and soul; making 9 understandably the number for eternity.

After His resurrection Jesus Christ appears to the disciples and apostles 9 times. There are 9 gifts of the Spirit: knowledge, faith, gift of healing, to operate miracles, prophecy, discreetness of spirits, tongues and to interpret them. There are 9 fruit of the Spirit: love, joy. Peace, patience, kindness, goodness, truthfulness, gentleness and self control.