Mark 4:20

‘And those are they that were sown on the good ground, such as hear the word and firmly receive it, and bear fruit thirtyfold, sixtyfold and a hundredfold.'

This is the climax of the parable to which all else has been leading. There are those in whom the seed sown will bear fruit, and that in abundant measure, because they firmly receive it. The magnificence of the yield draws attention to its importance in the parable. As every farmer knew, some seed sown would produce a harvest. And that was why he went on sowing. Thus there were those who would hear the word, and would take it to their hearts so that it could give them new life and mould their lives, and there would be fruit in abundance.

We should note here again Isaiah 55:10, “As the rain and the snow come down from heaven, and do not return there, but water the earth,  making it bring to birth  (the Hebrew is yalad in the hiphil, almost exclusively used of the birth of living creatures) and sprout, giving seed to the sower and bread to the eater, so shall My word be -- '. Jesus does not mention rain in the parable but it would be everywhere assumed by his hearers, and it brings to new life those who receive it. To Isaiah the life-giver was the rain of the word of God and only secondarily the seed, to the Spirit empowered Jesus it was the seed sown in the power of the Spirit that was the word of God, but both represent the word going forth to fulfil God's purposes.