A "blank cheque" means a signed cheque with the amount left for the payee to fill in.
Figuratively, it means an unlimited freedom of action.
So, if we were ever handed a blank cheque, what is the amount that we would write in, presuming that whatever amount we write in will be honoured and given to us.
That would sound like too good to be true and we know in reality that it won't ever happen to us.
In the gospel, Jesus said that anything we ask for from the Father will be granted in Jesus' name.
We have asked for many things in prayer, and some have been been granted, and others will probably be granted.
But if we were given a spiritual blank cheque, what would we really ask for.
But the question is not what we would ask for. Rather it should be that do we know what God really wants to give us.
God wants to give us the Holy Spirit, which He will send in Jesus' name.
When we have the Holy Spirit, then we won't ask for anything else.
Because the Holy Spirit is the greatest gift of love from God which is given in Jesus' name.
With the Holy Spirit in us, we will have everything which money can never buy.