Mat 16:18 - I will build my Church

18 And I also say to you that you are Peter, and on this rock I will build My church, and the gates of Hades shall not prevail against it.

“You are Peter” = Gr. Petros, masculine = A huge stone
“on this rock (Petra), feminine” = A massive rock, eg. mountain range.
The church must be build on living stones. The Church is built on people who confess that Christ is the Messiah.

See also

1 Peter 2:4-5
4 Coming to Him as to a living stone, rejected indeed by men, but chosen by God and precious, 5 you also, as living stones, are being built up a spiritual house, a holy priesthood, to offer up spiritual sacrifices acceptable to God through Jesus Christ.

It is one thing to receive the Lord but another to commit yourself to Him. Because we have passed from death to life, we are fit to be living stones in the Church.