John Gill Commentary 1 Samuel 18:29

"And Saul was yet the more afraid of David; and Saul was David`s enemy continually." — 1 Samuel 18:29 (ASV)

And Saul was yet the more afraid of David
Because the Lord was with him, and his wife loved him; so that he feared he should never be able to accomplish his designs, and that this marriage, which he intended as the means of his ruin, would pave the way for his ascending the throne:

and Saul became David's enemy continually ;
was every day giving fresh evidence of his enmity against him; before it was by fits, and at certain times, there were some intervals; but now enmity was rooted and habituated, and was constant and continually showing itself.