Historical Rules · 20 November 2020
Rule 702.46b
Official source text from the 20 November 2020 Rules release
You can’t choose to use a splice ability if you can’t make the required choices (targets, etc.) for that card’s rules text. You can’t splice any one card onto the same spell more than once. If you’re splicing more than one card onto a spell, reveal them all at once and choose the order in which their effects will happen. The effects of the main spell must happen first.