Sentence:  He spent concentrated weeks putting his two figures together : a Mary who would be young and sensitive , yet strong enough to hold her son on her lap ; and a Jesus who , though lean , <WSD>was</WSD> strong even in death - a look he remembered well from his experience in the dead room of Santo Spirito . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)